invenio.exe.menu: Menu extension created

* Adds an extension which provides menus organised in a tree structure
* Menu items are created through decorators
* Menus can be displayed in templates

Signed-off-by: Krzysztof Lis <krzysztof.lis@cern.ch>
WebTag: example usage of MenuAlchemy
invenio.ext.menu: code style improvements
invenio.ext.menu: usage in blueprints
invenio.ext.menu: fix for template
invenio.modules: moved models
invenio.modules: moved blueprints
invenio.modules: renamed models imports
invenio.modules: renamed blueprint imports
model, blueprint: Makefile.am removal
managers discovery quick fix
blueprints loading
factory cleanup
invenio.modules: moved admin_blueprints
invenio.modules: moved user settings
invenio.modules: moved template context functions
WebTag -> invenio.modules.tags
dashboard: new module for user settings widgets
invenio.base.manage: moved from inveniomanage uses setup.py
user_settings removal