Fix always switching back to mgun in Q3 controls menu

Caused by 120e296a74b0317f29d7f516d904bdc70f71b006.
Fix Gauntlet barrel axis in UI

UI's PositionRotatedEntityOnTag is different than CGame's and
UI has switched pitch/roll for Gauntlet/BFG axis to get it to
look like /close to/ how it looks in CGame.

Making UI use the same *PositionRotatedEntityOnTag and axis as
CGame fixes the Gauntlet blade being wobbly in controls menu.
mint-arena: Allow any weapon to use client color, not just rail gun

The color is only used if shader uses rgbGen entity. No reason to
limit to railgun. No other Q3 weapon shaders use rgbGen entity,
so doesn't change visuals.
mint-arena: Fix weapon fallback for missing model in UI
mint-arena: Try to load barrel for any weapon in UI

This is what is done in CGame.
mint-arena: Only colorize rail impact mark

It effects all impact marks, only meant for railgun so change it back.

Partially reverts d3f2f4c96c65771c5910557821203423f52a9ff7.
mint-arena: Use BG_NumItems() instead of bg_numItems

bg_numItems is still used in bg_misc.c
mint-arena: Move key catcher to CGame VM
Merge remote-tracking branch 'upstream/master'
Mecwerks-Logic: Fix conflicts from last pull.
Mecwerks-Logic: Apply zturtlemans patch.
Mecwerks-Logic: Modify a few things.
Mecwerks-Logic: Move this back.
Mecwerks-Logic: Hardcoded weapons.c
Bots are still broken.