Fix screens not triggering read-/writeCell hooks

Fixes #33
Merge pull request #35 from awilliamson/I30

Added getMaterial & setMaterial to ents (inc holo)
Merge pull request #67 from awilliamson/I41

Hologram Lib - Static create, burst convar, libs_sh -> libs_sv move.
Merge pull request #55 from Xandaros/hispeed

Fix screens not triggering read-/writeCell hooks
Merge pull request #68 from awilliamson/I44

Hologram SetRenderMode & RenderGroup Fixes
Added setBodygroup & setSkin.

Fixes #25
Removed SF.CheckType( self, ents_metamethods ) from setBodyGroup & setSkin.
libs_sh/ents.lua
See #32