Document all overridden API functions

[vtrlx]

LuaGObject has inherited the existing overrides from LGI. These overrides are presumed to exist in order to make it easier to use certain functionality in a Lua-esque manner, but documentation on them is lacking. The problem with these overrides is that because they often shadow existing functions exist on various classes, someone working off of C API documents will find themselves taken by surprise as methods won't work as advertised from LuaGObject. This trial-and-error situation can make LuaGObject quite painful to learn if you aren't wholly dedicated, and should be rectified through thorough documentation of overrides.