Idle animations & Admire Gloves Animations Redo

[ampreeT]

Changes:

• Added idle animations using prop_dynamic and built-in mp animations
• Rebuilt admire gloves logic to work while being unarmed
• Removed placeholder crowbar in the first levels of the Black Mesa campaign

Fixes #76

[Alienmario]

There's some room for optimization, esp. in high frequency callbacks like PreThink. IsValid can at places be replaced with != NULL_CBASEENTITY check. I find IsValid most useful for asynchronous programming; for same callback property read / sdk call you don't really get "invalid entities", but null (-1).

More importantly please make sure playermodel changes are reflected. If you need something to test with: ModelChooser