Release resource file memory after deleting

[Bl3nd]

Clear resource classes, class bytes, and files after deleting directory from resource list to clear memory. In response to issue #482.

[threefusii]

always forcing System.gc() may not be a good idea especially for a lot of RAM and slower processor single-core speed. maybe hide it behind an (enabled by default) option?

anyway, there's always -XX:+DisableExplicitGC

[Bl3nd]

I totally understand the System.gc() concerns you have, I will try other ideas I can come up with.

[Bl3nd]

Closed PR to further address memory issues when deleting a resource (for now). Even when deleting and clearing using the above code (without gc) it keeps the deleted ResourceContainer in memory and adds new instances using either reload or add.

[Konloch]

I pushed an update to help with this - aea66fe - this should resolve the reference issue