Re-instate pretty double angle bracket symbol

Prefer these over two single large angle brackets, not sure if they were
lost in a merge or intentionally removed.
Alternative solution for angle bracket display. looks best on Window Mac, while linux boxes without MS fonts installed see slightly larger thinner arrows
Commit issue #624 - problem still exists wrt opacity slider
VIT Clear button for date picker
VIT Date Picker clear button. Fixed tests and changes as per review.
Clear filter button changes as per review
Using Grails method to link to image relative path on landing page
Map drawing polygon type selection

Allows the user to select what type of bounding area they want to draw
on the map, options being a bounding box, polygon or none for navigating
the map. There are currently two instances of the control, one on the
AODAAC subset panel and one on the WFS subset panel, they cannot stay in
sync at the moment because the FilterGroupPanel is re-created on every
layer swap.
Added newline to end of file
Changes based on review
Correct relative paths, the Grails way, for every link in a GSP
Merge pull request #682 from aodn/map-polygon-type-control

Map drawing polygon type selection
Introduced `SpatialConstraint` control - common to geo facet and the main map.
GeoFacetMapToolbar now uses the new SpatialConstraint control.
Combo filter panel, option for all filters to be applied to the map
panel
Merge pull request #680 from aodn/landing_image_path

Using Grails method to link to image relative path on landing page
Merge pull request #685 from aodn/issue_#624

Commit issue #624 - problem still exists wrt opacity slider
Changes to code style as per review
Merge pull request #684 from aodn/spatial_constraint_control

Spatial constraint control
Refactored bbox as string conversion to openlayers bounds.