Add ability to use actual given folder as the pp_home folder. The previous behavior is still supported (pp_home as a subfolder of the given folder, or ~/pp_home, or fall back to pipresents/pp_home.
When I first started using PP, it took me a good 10 minutes (at least) of trying to figure out why PP wasn't using the folder I told it to. I don't remember if I read through the long manual or the long log to figure out the problem.
Actually, now I have a real reason to use the specified folder instead of a subfolder, because the latter would add a whole layer of folders for me, which would be empty except for the pp_home folder.
! Fix parsing of image filter
* Also improve the parsing so the filter name doesn't have to be all caps