Add plugin reflection remapping. Closes #13.

Calls to getDeclaredField("") can now be remapped by
enabling mcpc.plugin-settings remap-reflect-field in
bukkit.yml. This is off by default for now but you can
turn it on to potentially improve plugin compatibility
(NoSuchFieldExceptions).

Methods and classes accessed through reflection are not
remapped by this setting. Additionally, only string
access to fields are remapped. More complex usages of
reflection in plugins is not yet handled; only the simple
(yet most common by far) case of string literal fields.

Affects #49, #77, #85, #88, #93, #126, #127, #131