WUI: initial commit of base perun-wui module

Perun's GUI implemented with usage of bootstrap and GWT.

- All features are only partially implemented, e.g. on some objects.
- Lots of features are only for testing (to decide about their future).
 - Contain a lot of sources from original Perun's GUI in order to work with current
development version.

Will probably stay:

- error-proof and unified getting of values from JS objects (PerunBeans)
- simplified API for calling RPC (static methods)
- better building of each GET/POST call (think about using cache, default timeout etc.)
- better usage of JsonEvents (todo default actions ?)
- auto disable active elements when action is running (map elements to tables)
- unified implementation of DataGrid (todo oracle support for filtering)
- one page layout (use links to navigate, but with js action)
- ColumnProviders to automatically build tables for each PerunBean including decisions like sorting
- Single implementation of clickable cell to point to object details (select objects by click)

To decide and TODO:

- when to use modals, default actions, colors ?
- colored buttons ? (for administrative part less colors)
- loader widgets (split to GUI, page, table, custom error handling)
- decide about informative messages (position, (auto)dissmisable, error reporting)
- find out proper way of using UIBinder to split design and function code.
- make this module as base with only "test" pages to provide functionality for
  future simple "apps" and later for administrative GUI redesign.