Updated build script.

- Latest versions for Android build tools and support libraries
- Java 7 compatibility
Created XTimeWebService client class.

New approach to consume the web service, should replace the assorted XTimeRequest classes eventually.Uses OkHttp for increased developer happiness.
Created authenticator for account management.

The authenticator supports account type 'xtime' and auth token type 'cookie'.

Only supports adding accounts and getting auth tokens at the moment. No account editing or other advanced stuff.
Removed old login activity

No longer used because of new authenticator flow.
Added call to get week overview from XTimeWebService.

We have to explicitly pass a cookie, because cookies are complicated.
Created SyncAdapter that gets the latest week overview.

Also requires a (stubbed) content provider. Next step: actually storing the content.
Added year and week to XTimeOverview.

Makes it possible to identify the time sheets in the database.
Implemented XTimeProvider for time registration data.

 The structure is inspired by the Google IO 2014 app. The SQlite database contains three tables: time_sheets, time_sheet_rows, time_entries. There is a separate XTimeContract class that contains the database schema contracts, with column names and URIs.
Updated sync adapter to use the XTimeProvider for storage.
Load data from content provider instead of HTTP.
Merge pull request #7 from Smuldr/fancy_sync

Fancy sync