Add file operation functions

[arthur-shaw]

Objective 🎯

Add file operation

User stories 📇

After a user downloads SuSo data, there are several other operations that need to occur and that, currently, need to come from hand-crafted code:

• Delete files from previous download
• Unpack zip files into appropriately named folders
• Combine data files
  • Combine value labels
  • Signal incompatibilites (e.g. conflicting variable and/or value labels)
• Write combined data frames to disk

Tasks ⚙️

Write functions to:

• Delete old files
• Unpack zip files
• Combine value labels
• Signal incompatibilities in labels and in structure of files
• Combine data frames
• Write data frames to disk in user-specified format (i.e., SPSS or Stata)

Documentation ✍️

• Create section in reference index page
• Write vignette on working with [AREA]