Make default filters configurable

[acorbi]

Apart from the additional filters that can be added to the tabular pages filter box, there are a series of filters that are added by default.

in order to achieve a much more flexible layout for partners, we should provide the option for editors to enable/disable the default filters in the settings of the corresponding tabular page.

This task consists on adding a series of checkboxes to the additional filters metabox which would allow editors to toggle the following default filters:

• language (odm_language)
• country (odm_spatial_range)
• taxonomy (odm_taxonomy)