Added get/setTextProperty() to Text, fixed TextFormatAlign and removed a...

...lignConv (no longer needed)

The Text class was missing a way to get/modify internal `TextField` and `TextFormat` properties, so `get/setTextProperty()` have been added.

I've also removed `alignConv()` as now the correct `TextFormatAlign` implementation gets picked up by conditional compilation.

Minitest: https://github.com/azrafe7/HaxePunk-minitests/tree/master/SimpleTestTextProps