update: correct menu item category view id (issue #607)
simplify deleteObsoleteFiles() (#620 related)
fix detcat_num (issue #625)

On old categories view it must be set to 0, on categoriesdetailed view it is already set so 0 is overwritten by original value.
altered thumbnail scaling (issue #553)
- ensure full image is inside max. area
- don't scale up
- css correction
altered calendars (issues #622, #621, #551)
added new text COM_JEM_TITLE_SHORT, COM_JEM_VENUE_SHORT, COM_JEM_TIME_SHORT, COM_JEM_WHAT
frontend calendar views: changed "label" (issue #624)
...to "text-label", not found in any css
recurrence: check all events of series on auto-creation (issue #626)