* increase target API level to 23 (Android 6), which makes Android 6-style permissions mandatory
* AUTHENTICATE_ACCOUNTS permission is only required up to API level 22
* new activity: PermissionsActivity which shows missing permissions and provides buttons to request them
* DavService: Android shouldn't send a null Intent, but sometimes it does, so implement null check
* LocalTaskList: tasksProviderAvailable may return true on API level 23+ even if permissions are not sufficient
* SyncAdapterService: show a notification (with Intent for PermissionsActivity) when permissions are not sufficient
* when creating accounts, set OpenTasks sync always to true if API level is 23+ (even if OpenTasks is not installed [yet])
* update Lombok
* new setting: only sync in WiFi (or when sync is triggered manually)
* new setting: only sync in specific WiFI (by SSID)
* lower default sync interval when account is created to 4 hours (was 1 day)
* version bump to 1.0.6
* AccountSettings$AppUpdatedReceiver: check for migrations only when package is replaced
* SyncAdapter: move DB helper from service to SyncAdapter to prevent databases from being closed too early
* Manual sync button: run sync immediately (without queueing)
* handle and show OutOfMemoryErrors correctly (they're not Exceptions)
* use db.beginTransactionNonExclusive() because WAL is enabled
* set calendar VISIBLE=1 AND SYNC=1 only at creation and not at every sync
* update PendingIntent of service refresh notification
* use last path segment as collection display name if there's no DAV:displayName
* add Contacts Provider Settings again to show contacts without groups in all clients (bluetooth cars etc.)
* add ACCOUNT_NAME and ACCOUNT_TYPE when creating calendars
* close TaskProvider when checking for its presence
* when TaskProvider is not available/accessible, explicitly disallow task sync at account creation
to prevent further crashes
* try to handle OutOfMemoryError
* version 1.0_2
* add InvalidAccountException for invalid (=not existent/invalid settings version) accounts
* handle invalid accounts properly
* HttpClient: add constructors without Account when authentication is not needed
* drop upgrade compatibility for accounts without version (version<1)
* re-initialize logger in :sync process after changing the settings (IPC using broadcast)
* move settings from SharedPreferences (which is not multi-process-safe) to ServiceDB
* logger: show exception details
* settings: show debug info
* honour calendar-proxy-read/write-for property
* ignore errors when quering member groups for home sets
* remove home sets and collections from the service database not only on 404, but 403, 404 and 410
* fix crash bug when <displayname> was defined, but empty
* add startup dialogs (F-Droid: donations, Play Store: DRM bug, OpenTasks not installed)
* allow to reset hints/startup dialogs
* AccountSettings: fragment as inner class of activity
* add account setting + GUI: restrict time range in the past
* add support for restricted time range VEVENT synchronization
* fix bug in handling changed exceptions of recurring events
* move AccountSettings up to package context
* HttpClient: take authentication from AccountSettings in the constructor
* App: provide global instance of MemorizingTrustManager
* App: provide global Java logger, optionally with verbose and external file logging
* LoginCredentials: moved from inner-class into setup package
* CalDAV/CardDAV resource list views now always contain all elements without scrolling (NonScrollingListView)
* synchronization action in activity now overriddes system sync settings
