Merge pull request #497 from bergerkiller/master

Fixed isMaterial documentation
Removed unused and obsolete isClickedBlock parameter

Signed-off-by: Irmo van den Berge <bergerkiller@gmail.com>
Can't use remove on unmodifiable sets
Null check hardening
Merge branch 'master' of github.com:SpoutDev/SpoutAPI
Added canSet method

Signed-off-by: Irmo van den Berge <bergerkiller@gmail.com>