Polish/Revamp recurring event picker

This is how the recurring event picker looks right now:
![7671aa96-9d4f-11e3-85a6-f3cd700ce008](https://f.cloud.github.com/assets/15332/2292226/47b986c6-a054-11e3-8b53-14d4b7292bfa.png)

This set of patches removes the fragment hour-minute-picker, enhances the date picker widget to ask only for dates and uses that into the recurring-task-picker fragment.

Some enhancements were required, and the Javascript for the datepicker was simplified, so that for example the initial server-side date can be provided as data-attributes instead of having the Java code spit put Javascript snippets (it is more "declarative" now). Also some Javascript was used to make the radio buttons disable the part that is not selected right now.

This is how it looks now:

![screenshot from 2014-02-27 15 44 13](https://f.cloud.github.com/assets/15332/2292231/58ad48fa-a054-11e3-82c1-8fd8cd28d823.png)