Console: Simplify registerFunction

It seems like it's possible to call methods via Reflect.callMethod
without specifying their object (and passing null instead), which
simplifies the process of registering a function as well as the call()
logic.
Merge branch 'texture_atlas' of https://github.com/Beeblerox/HaxeFlixel into dev_console
Console: Integration of advanced logging and more

- the console now uses advanced logging
- removed leftover trace() from Log.add()
- fixed html tags in Log.add()
- fixed switch-statement in ConsoleCommands.help()
- made it compilable with FLX_NO_DEBUG set
Merge pull request #375 from Gama11/dev_console

Console: Simplify registerFunction()