gwt emulation for class hasAnnotation.
Fixed for gwt compile errors under gradle caused by inclusion of
generators.
Fixed missing reflection gwt includes causing exceptions at runtime.
Support for class annotation ```@Mapper``` on gwt.

Support for class annotation ```@Mapper``` on gwt. Does not support
mapper fields failOnNull and injectInherited.
Added all systems and managers to annotation by default.

Added all systems and managers to annotation by default. Required for
```@Mapper``` injectInherited
Merge pull request #70 from DaanVanYperen/cherrypicked-fixes

Support for @Wire on classes + gwt&gradle compile exception fix.