TTT: Added Scoreboard hooks

Added hooks:
"TTTScoreboardColumns" - Two arguments, Panel and Enumeration. Return nil.
"TTTScoreboardMenu" - One argument, Panel. Return PreventOpen (Boolean).

Added enumerations for TTTScoreboardColumns hook:
TTT_COLUMN_HEADING - Column headings
TTT_COLUMN_ROW - Column row/data
TTT_COLUMN_BACKGROUND - Column background (Darker columns)

Added functions PANEL:AddColumn( label, func ) to scoreboard panels.
TTT: Simplified "TTTScoreboardColumns" hook

TTTScoreboardColumns now has only one argument, the panel.
Returned label now has value lbl.IsHeading to determine if it is the column heading.
Dark columns now grab the data from the TTTPlayerFrame panel.
Yet another crash exploit fix

This time caused by wheel_rx 999999999999999
Remove empty/broken panels from derma_controls

Some panels just have no reason to be in there.
Also, fixed the preset editor to some extent.
Fixed some issues with constraint tools

* Fixed Muscle tool "Start on" option not doing anything
* Fixed Elastic tool creating a rope even if no elastic constraint were
created
Merge pull request #627 from robotboy655/wheelexploit

Yet another crash exploit fix
Merge pull request #628 from robotboy655/panels

Remove empty/broken panels from derma_controls
Merge pull request #629 from robotboy655/constr

Fixed some issues with constraint tools
Minor updates to Post Processing Effects

* Added presets for all PP effects
* All convars now save over sessions
Merge pull request #620 from MyHatStinks/master

TTT: Added Scoreboard hooks
TTT: Clean up around new scoreboard hooks
Fix halos and lamps
Merge pull request #631 from robotboy655/patch-1

Fix halos and lamps
Merge pull request #630 from robotboy655/pp

Minor updates to Post Processing Effects
Added new NPCs and merged EP2 NPCs
Added Jalopy
Merged Magnusson and added Alyx Gun
Delete game_ep2.lua
Fixed the Jalopy going into the chairs category
Find out how to add helicopter grenade skin 2