GUI: refactored and optimized gwt modules

- Based on knowledge from WUI project, gwt now uses inheritance:

- standard "mvn clean install" builds devel version of gui without sourcesMaps
  => speed up compile
- "mvn clean install -Pproduction" builds production version of gui without sourcesMaps
  but fo all browsers. Now uses xsiframe linker.
- for local development pick "-dev" modules, they build also sources map, but support only
  two browsers.

- Moved .gwt.xml files to ensure visibility to gwt compiler.
Merge pull request #492 from zlamalp/guigwt

GUI: refactored and optimized gwt modules