Support additional variations of "CHECKSTYLE:OFF" comments

The maintains support for the style commonly used in files currently:

//CHECKSTYLE:OFF - optional comment here
...
//CHECKSTYLE:ON - optional different comment here

But also adds the following:
Disable a specific rule: //CHECKSTYLE:OFF: CheckstyleRule
Disable checking for the following line: //CHECKSTYLE:IGNORE
Disable a specific rule for the following line: //CHECKSTYLE:IGNORE: CheckstyleRule