* detect CardDAV VCard version support using supported-address-data + test
* account setting for supported VCard version
* don't ask for calendar details when querying CardDAV collections
* don't ask for address book details when querying CalDAV collections
* ez-vcard update to 0.9.5 (fixes#268), adapted exception handling
* refactoring: unnecessary DavProp prefixes removed
* fix issue when first upload fails (fixes#233)
* show debug settings menu item in main activity
* update ETag in local database when a PUT request returns an updated ETag, meaning that
locally created/updated records won't be downloaded from the server immediately after the upload
* force debugging options for resource detection (because there's no way to turn them on until there's an account)
* provide "report issue" button in debug settings
* provide CONTRIBUTING.md, including instructions on how to report issues
* increase socket timeout from 20 to 45 seconds (hopefully fixes#237)
* previous commit: increase total simultaneous connections to 3 (2 per host)
* preference screen for debug settings
* allow to disable HTTP compression
* verbose network logging only when activated
* single HttpClient for all threads (before: single HttpClient per adapter)
* bump version to 0.5.13-alpha
* store unknown VCard properties in an extra column and load them when generating a new VCard (closes#118)
* upgrade to ez-vcard/0.9.3 (fixes sync error reported via Play Store)
* (re-)enable stale collection check, RetryHandler to retry idempotent CalDAV/CardDAV requests (hopefully fixes#225)
* always set FN/display name (take organization if no structured name is available) (hopefully fixes#227)
* Account settings are now read/set using AccountSettings
* AccountSettings upgrades old account settings when necessary
* Settings v1: use absolute URLs instead of paths and discard principal path
(required for future implementation of well-known URIs)
