Added support for GWT -- including Reflection wrapper

Fixes #56 - GWT compatibility

- Added reflection wrappers to `artemis-odb` module
- Created a new module `artemis-gwt` which handles GWT emulated classes as well as handling reflection.
- removed `readFileContents` from Utils as it was causing problems with GWT compilation.
- `@Mapper` annotations are still fully respected in GWT compiliation
- reflection classes from libgdx were used and enhanced (they did not support annotations on fields).