A first few experiments with a UI for omni
Merge pull request #9 from daniel-kun/master

Update omni-forge from master
omni forge sandbox: Refactored the literal_expression view/edit-widget to be more generic.
Created a entity_widget_provider registry (currently only populated for literal_expression_view)
Extracted the classes entity_base_widget and generic_entity_editor from sandbox.hpp/.cpp and moved them to omni-ui
- Extracted the classes entity_widget_provider, entity_placeholder_widget, literal_expression_view and entity_edit_widget from sandbox to separate .cpp/.cpp-files in the omni-ui project
- Cleaned up the qmake .pro-files to not cause warnings when compiling
Completed the sandbox ui
A few fixes and improvements to the sandbox framework and the literal_expression sandbox demo
Added a search field (shortcut: Ctrl+F) to the list of demos
* A small refactor regarding entity editors (renamed entity_edit_widget to entity_toggle_widget, added entity_widget_provider_base, added an entity-to-text-converter to generic_entity_editor)
* Added a new variable_declaration_expression sandbox demo - not finished, yet. The initialization expression is not implemented.
Merge remote-tracking branch 'remotes/origin/omni-forge'