Editing profile: No change warning on leave.

[Gryzor]

Objective

• Prevent data loss when the user inadvertently hits back or wants to leave the profile edition with unsaved changes.

Description

• To limit the number of changes to the existing codebase, I merely re-used the same method used by save() in the ViewModel to decide whether to make a network request or simply return the profile as-is.
• A bit of code juggling around in the ViewModel and I was able to use the logic for all the encoding of each profile field (Which is what the ViewModel caches in memory). Thanks @Lakoja for improving this in the VM.
• A couple of internal data classes used as helpers to move all the fields around (now that they are no longer used in one single place) were introduced.

Potential Optimizations

• The profile encoding is done twice (once for checking, and then again if the user has to actually save it). I'd say this is a negligible price to pay, since the alternative would be to create a different set of comparisons and/or keeping another profile in memory for the purpose of comparison.

Visual Improvement

• I believe the Dialog is difficult to see, but it's being displayed with Tusky's theme. Perhaps there's a better style to apply in this case? (or maybe the edit profile activity shouldn't have the same background color as dialogs?!)

Issue

• Editing profile: No change warning on leave #3486