* new icons with 3D effect as required in Android Iconography Guide
* target SDK version updated to 20
* replaced UI directions left/right by start/end for RTL support
* Show "unnamed calendar"/"unnamed address book" instead of "null" in "Select collections" fragment
* "Add account" button now directly adds DAVdroid account
* .svgz for "How DAVdroid interacts with other components" added to doc
* 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)
* allow to enter account name at the end of account setup (fixes#13)
* advise user to enter email address as account name (closes#24)
* support for iCal TRANSP (availability free/busy field)
* create better UIDs using iCal4j UidGenerator and Settings.Secure.ANDROID_ID
* better ORGANIZER/ATTENDEE support, but there are big Android issues yet
* various improvements and bug fixes
