Allow filtering by AI file

[jimmcnulty41]

Right now, we run MOLT on every file in the source folder. Sometimes you just want to molt a single file

[jimmcnulty41]

Alternatively, we could have a flag for MOLT so that it checks for existence before rendering out a new version of something. When we haven't made any changes to the After Effects file, and instead, we've just added a new source, we would just run with a "--no-overwrite" flag