Snooze and calendar in task editor
 * renamed pikaday* to calendar elsewhere except in LESS
 * removed calendar from snooze.html
 * removed other item dependencies than date

Bugfixes and refactoring:
 * removed openEditor and closeEditor functions from drawerDirective
 * renamed closeEditor to endEdit, <close|open>OmnibarDrawer to <close|open>Editor
 * added clear titlebar text icon to all editor types
 * isCurrentWeekValid will returns 'true' so that week is valid if there is no 'today' in it