Made submit button more prominent.

Added "btn-primary" class. Fixes #13 (partially).
Refactored the refresh part into a separate function.

(This way we can call it later on from a select-has-changed event).
Replaced submit button with automatic reloading.

The submit button is now a spinner.
A form change automatically submits the form.

Fixes #13.
Updated changelog
URLs in the popup now open in a new tab.

Fixes #17

I don't like this myself.
Improved FilterPage's breadcrumbs.

Fixes #18.
Further breadcrumb improvements.

Updated dependency on lizard-maptree to 1.9 minimum as that
adds get_absolute_url to maptree's category model.
Using {% static %} instead of hardcoded url
Merge pull request #19 from lizardsystem/reinout-oase-fixes

Various UI fixes to the filter page