Delete static-assert.h
Split ThisPlugin into two classes
Enclose unlimitedfs code in namespace unlimitedfs
Rename some core APIs and deprecate the old ones

Renamed functions:

sampgdk_initialize -> sampgdk_init
sampgdk_finalize -> sampgdk_cleanup

New functions:

sampgdk_init_plugin
sampgdk_cleanup_plugin

The old functions are maintaied for binary compatibility and will be
removed in next major release (4.x).
Add SAMPGDK_DEPRECATED macro