feat: allow custom output folder name

[JamesHabben]

• note: CLI and framework functionality was already in place
• GUI now has textbox to allow customization of output folder name
• guards illegal folder name characters in both CLI and GUI
• guards to prevent overwriting existing folder in CLI and GUI
• illegal character file/folder functions moved from ilapfuncs to new modularized /leapp_functions/ path
• ilapfuncs imports old functions from new path to keep backwards compatibility
• left commented out def lines in ilapfuncs to note they have been moved

[JamesHabben]

[stark4n6]

@JamesHabben do we want the label to say something like "Custom Folder Name (optional)"?

[Johann-PLW]

@JamesHabben do we want the label to say something like "Custom Folder Name (optional)"?

I'm not sure it is relevant to rename the label as it is the name of the folder where the reports will be saved: Output_path + folder_name.

By default, it uses the convention we've always used: leappAppName_Output_YYYY-MM-DD_NameOfTheDay_HHMMSS.
By the way, I think we could remove the name of the day.

[JamesHabben]

I agree with removing the day name. Makes it extra long for sure