FolderNameFilter handles messages in multiple folders.

[daewok]

The FolderNameFilter used to look only at a message's primary folder (message.get_filename()) when deciding which tags to apply. This change allows the filter to look at all folders that a message exists in when applying the tags.

This was done by retrieving all filenames using message.get_filenames() and adding the appropriate processing to handle the list of file names.

This change would be especially useful for those using GMail to add tags to their messages.

[ryneeverett]

Needs rebasing, but otherwise works great!

[GuillaumeSeren]

hey @daewok @ryneeverett 🍻 🍻
I use Gmail and so this would be neat to have, can you rebase the patch please ?

[varac]

hey @daewok @ryneeverett  
I use Gmail and so this would be neat to have, can you rebase the patch please ?

Yes please! I'd like to have this included into afew as well.

@GuillaumeSeren If @daewok is not responding, could you pls rebase and merge yourself ?
I just rebased the foldername_filter on top of current master locally without any problem.

[GuillaumeSeren]

@varac Hey, I have rebased the commit so I close this PR in favor of the new one -> #145