Add @API to BlockDefinition so that modules can define block families
Merge pull request #935 from Josharias/EnableFamilyFactory

Add @API to BlockDefinition so that modules can define block families
Add relative side convenience method
Merge pull request #936 from Josharias/AddRelativeSide

Add relative side convenience method
Remove lwjgl dependency from Performance Monitor
Move headless classes into headless subsystem
Merge pull request #939 from mkienenb/PR-PerformanceMonitor-lwgjl-dep

Remove lwjgl dependency from Performance Monitor
Merge pull request #940 from mkienenb/PR-consolidate-headless-code

Move headless classes into headless subsystem
Merge remote-tracking branch 'upstream/develop' into behavior
Only one global entity can be exist