Improved import_package functionality - now import can remove widget's outputs,inputs and options which are not beeing used.

First approach to include static_image field in the treeview and widget. It works but still needs to be rechecked/redone by the chief architect :)

Added import/export functionality for widget definitions (for models: AbstractWidget, AbstractInput, AbstractOutput, AbstractOption, Category).
Three managment functions added:
- export_package
- import_package
- renew_uids
Help included should be enough to understand each functionality.
Everithing is 'quite' thoroughly tested, however, I STRONGLY suggest database BACKUP before doing commands import_package or renew_uids. export_package should be safe.

Merge branch 'dev_latino' into dev (last merge since separate dev_latino branch will be terminated afterwards)

New dev branch to be merged with dev_latino - nothing changed based on previous version (empty line removed from library.py in order to be able to commit)

Corrected behavior of "Run" context menu command in case of being executed on already successfully executed widget.
Now behavior is identical as in the command "Run only this" -> the widget is first reset and then rerun.

Corrected behavior of "Run" context menu command in case of being executed on already successfully executed widget.
Now behavior is identical as in the command "Run only this" -> the widget is first reset and then rerun.

Conflicts:
	workflows/static/css/images/help.png
	workflows/static/css/jquery.contextmenu.css
	workflows/static/js/new-script.js
	workflows/urls.py
	workflows/views.py

Added context menu on treeview widget repository for categories and widgets to directly access admin console.
Reorganised context menu
Run widget with hieraricaly running all predeccessos
Reset widget
Reset workflow

Conflicts:
	workflows/library.py
	workflows/visualization_views.py

Added alter table widget for editing orange tables. Still TODO: for discrete variables a dropdown list of legal values should appear when editing.

Conflicts:
	workflows/visualization_views.py

Conflicts:
	workflows/urls.py
	workflows/visualization_views.py

Moved table styling to style.css to avoid duplication. Kepner-Tregoe widget: moved normalization (which is now optional) to the UI; moved the form elements to a nice table. Sens. analzsis widget: added nicer radio buttons.