Update installer to organize packages by categories

[sara-rn]

Update installer so that after the initial form to set up the environmental variables a new window displays all the packages grouped by category.

• The packages from config.xml need to be selected by default.
• The option to select all the packages from a specific category, for example if the category is a checkbox, doesn't work well as the checkboxes need to be generated dynamically. Currently each category is displayed in a label.

Closes #578

[Ana06]

@sara-rn the installer here is broken because #671 broke the installer. Please rebase after #675 is merged so that the code works.

The fist UI window (install customization) is missing a next button, so I couldn't test the categories page:

Please address this issue so that I can review the new window as well.

Remember adding labels to PRs (in this case enhacement is appropriate) and to add the issue the PR closes to the PR description (this PR should address #578).

[Ana06]

If you catch the error, how can you continue to execute the rest of the code without categories?

[Ana06]

Make the installation of nuget consistency (same code structure) with the installation of other dependencies like boxstarter and chocolatey. Concretely: check if it is installed if possible, and print a message that is being installed and installed successfully instead of the output:

Name                           Version          Source           Summary
----                           -------          ------           -------
nuget                          2.8.5.208        https://onege... NuGet provider for the OneGet meta-package manager

[sara-rn]

@Ana06 there is no need to use Find-Package, therefore the installation of nuget or download categories.txt is not necessary. At the end of the feed from https://www.myget.org/F/vm-packages/Packages there is a <link rel="next" with the URL for the next packages.
The packages are selected and the Continue button adds the selected items to the config.xml

[Ana06]

@sara-rn I was not able to review the installer UI as the installer does not run correctly:

Get-Packages-Categories : The term 'Get-Packages-Categories' is not recognized as the name of a cmdlet, function,
script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is
correct and try again.
At C:\Users\flare\Desktop\install.ps1:491 char:27
+     $packagesByCategory = Get-Packages-Categories
+                           ~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Get-Packages-Categories:String) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : CommandNotFoundException

I think is because you have placed the code of Get-Packages-Categories after the use of the function (it needs to be defined before). Please ensure the code works as it otherwise make it the review difficult.

I also recommend you to add some screenshots when making UI changes.

[Ana06]

@sara-rn

@Ana06 there is no need to use Find-Package, therefore the installation of nuget or download categories.txt is not necessary. At the end of the feed from https://www.myget.org/F/vm-packages/Packages there is a <link rel="next" with the URL for the next packages.
The packages are selected and the Continue button adds the selected items to the config.xml

Seeing how complicated the code to use https://www.myget.org/F/vm-packages/api/v2/Packages?$filter=IsLatestVersion%20eq%20true is, I think the solution with Find-Package was better: much simpler code and easier to maintain.

[sara-rn]

@sara-rn I was not able to review the installer UI as the installer does not run correctly:

Get-Packages-Categories : The term 'Get-Packages-Categories' is not recognized as the name of a cmdlet, function,
script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is
correct and try again.
At C:\Users\flare\Desktop\install.ps1:491 char:27
+     $packagesByCategory = Get-Packages-Categories
+                           ~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Get-Packages-Categories:String) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : CommandNotFoundException

I think is because you have placed the code of Get-Packages-Categories after the use of the function (it needs to be defined before). Please ensure the code works as it otherwise make it the review difficult.

I also recommend you to add some screenshots when making UI changes.

I executed it without any issues, but when I switched to a different snapshot with Powershell version 5.1 I had the same error

[sara-rn]