make the setup of the date picker more declarative using data- attributes in order
to be able to share this setup with other parts of the code that will need a slightly
different picker like the recurrent selector.
It also saves us from outputing one <script> tag in the jsp tag implementation.
syncrepos: remove line break
use buttons instead of inputs
syncrepos: format the page
allow to disable date selection in addition to time
- if the datepicker date is disabled, disable the date part of the widget.
- always generate the hidden fields. StrutsDelegate::readDatePicker will
  reset _all_ your date to now() if any field is missing.
Revamp the recurring picker fragment to use the datepicker time component.
For this the RecurringDatePicker bean now is composed of DatePicker beans to
reuse functionality.
With some Javascript, the repeat-task-picker disables the cron frequencies that
are not being used.
Use String.equals instead of ==, this works only because we are lucky to get the
constants as input.
fixing checkstyle