FlxPoint support for log and watch / log security

- added `FlxPoint` support for `log` and `watch`
- added `formatFlxPoint()` helper function to `FlxU`
- added security feature to `Log.hx` to avoid inserting html tags

Tested and working. 

Closed my old pull request #355 due to merge conflicts and the `texture_atlas` version of `FlxG.log()` being more up to date.

I haven't tested the `_point` property of `FlxObject` again, but I assume it's still not working. It doesn't really matter anyway though if it's internalized like I suggested: #351