Fixed metadata synchronization

Realized the handling of metadata synchronization was flawed on 2 fronts:

1. Damn thing doesn't support keys with multiple values for a single post.
2. Kinda messed up how it split the metadata field list into individual lines properly (more than one resulted in a \r getting added onto it).

Anyway, it's all fixed and working properly now. Also made some improvements to the commenting on most of the PHP files.

Also, any input on a better way of syncing the metadata would be appreciated.