Pass correct format to JS widget

This fixes two issues:

1) The code didn't take into account that self.format will be ignored by
   Django if USE_L10N=True, unless a format was specified when constructing
   the Widget. Remedied by moving the code to render because the current
   language is determined at request time, not at object construction time,
   and looking up the correct format there.

2) The code couldn't handle date formats that include dots, like
   31.12.2014.

Fixes #1440.
Replace timepicker

with http://jdewit.github.io/bootstrap-timepicker/
revision f6cef44b5aecdf19704ea9b8c0af2b760ddef63b

The timepicker with sliders for hour and minute were just totally unusable
in our tests with customers.

This timepicker has some shortcomings though:
 - it doesn't support time formats. 24-hour hh:mm ought to be enough for
   everyone!
 - the maintainer stopped maintaining it

I included both the minified and non-minified files for convenience.
Replace datetimepicker

with https://github.com/smalot/bootstrap-datetimepicker
revision a68df421622c9fdcf4ba68ec6bcf0c2456c8d4df

In all our tests the time sliders under the calendar were always ignored.
Also this datetimepicker looks bootstrap and thus fits visually much more
into the rest of the dashboard.
Replace datepicker with the date part of the datetime picker
Replace timepicker with the time part of the datetime picker

One shortcoming is that the widget now shows the time in american format in
the header. (The format used in the input field is not affected and works
as we need it, supporting different formats.)
Display time in user- or locale-defined format in timepicker

From https://github.com/smalot/bootstrap-datetimepicker/pull/306
Concatenate into one JS file and load translations for datetime picker
Set correct language for datetime picker
Component for datetime and date widgets

This also selects the inputs that should have the date picker in a more
reliable fasion. The custom widget adds a data-oscarWidget attribute that
is used to select the elements to apply the widget to.
Add a component time picker widget

Currently oscar doesn't have time fields but we do and others can, too.
Remove duplicate ifs

Before, different widgets were used for each case, now it's the same
widget, so only one test is needed.
Merge branch 'machtfit-datetimepickers'

Conflicts:
	oscar/forms/widgets.py
Finish up datetime picker work

* Document new datetime picker in release notes.
* Update the tests to new format
* Fix some PEP8 issues