[API change] synchronize route combobox and current route directly via AlternativeRoutesModel rather than via RoutingLayer
no need to check for existance of routing model

* m_routingModel is always non-zero
remove RoutingLayerPrivate::showContextMenu()

* call MarbleWidgetPopupMenu::showRmbMenu() directly
[API change] remove RoutingLayer::routeDirty() signal

* have the RoutingLayer call RoutingManager::retrieveRoute() directly rather than relying on others to wire up the signal properly
introduce RoutingLayer::repaintNeeded() for requesting repaints (rather than calling MarbleWidget::update() directly)
emit themeChanged() _after_ map theme model has been updated
remove 2nd and 3rd column of MapThemeModel

* use Qt::UserRole+1 (mapThemeId) and Qt::UserRole+2 (description) instead
set role names only in declarative MapThemeManager
only translate celestial body name (but not the celestial body ID)
always use the sorted m_celestialListProxy
rename private slot
reuse updateMapFilter
when new map themes appear, only update celestial bodies list (and don't setMapThemeId() in addition)
expose celestial bodies model in MapThemeManager
Keep celestial bodies and map theme lists sorted. Always.
SVN_SILENT made messages (.desktop file)
SVN_SILENT made messages (.desktop file)