Organizer delete

add back delete options

• closes #294 (closed)
• delete single entries
• delete lesson
• delete subject
• single entry delete animation
• revert single entry delete animation
• revert multiple single entry delete animation
• revert delete lesson animation
• revert delete subject animation
• correct handling if lesson/subject is reverted to not show deleted single entry (because of it's "OLesson"-Subscription)
• implement odrawer_m_delete (Delete Menu)
• longpress on delete (default: single entry)
• delete options (single, lesson, 1-n subjects of your program selection)
• swipe drawer down to discard
• persist deletion (OSettingsBloc)
• slide to space animation
• optimize code so OCalendarEntries do not render >5ms (way too long)