Fixed internal object and DB inconsitencies for modified default groups

Fixed console errors for failed parent dependencies of default groups that already exist caused by fb11729547 consistency fixes

Made GroupManager.groups readonly to discourage overwriting it. Could still do with better encapsulation to prevent consistency problems if modified externally.

Added UpdateGroup method to GroupManager

Refactored Group handling of permissions and chatcolor to prevent inconsistent data
Notably:-
* AddPermission now does the right thing when passed the string "!permission"
* Converted ChatColor from method to getter / setter

Added RemovePermission to Group

Refactored GroupManager Permissions handling to ensure consistent data between DB and internal objects

Removed redundent AddGroup method in preference to a default value on the main method

Correct some tabs vs spaces

Added ParentName helper to Group

Fixed inverted parameters to error "Invalid parent {0} for group {1}"

TShockAPI/TShock.cs

@@ -172,7 +172,6 @@ namespace TShockAPI
 				Warps = new WarpManager(DB);
 				Users = new UserManager(DB);
 				Groups = new GroupManager(DB);
-				Groups.LoadPermisions();
 				Regions = new RegionManager(DB);
 				Itembans = new ItemManager(DB);
 				RememberedPos = new RemeberedPosManager(DB);