Merge pull request #4 from melenevsky/master

Changed add_filter trigger from click to change
added simple list filter support
added migration from simple list filters support
added related child fields support
fixed related fields support
marking newly added field as checked
fixed related fields support
added empty choices if option was not selected for field
fixed templatetag for errors displaying
skipping fields validation, if fields row was disabled
changed URLs reversing in case of custom URLconf
deleting fields from temporary filterset if row was disabled
reworked field adding and made it ajax powered, minor refactoring
Merge pull request #1 from boutdepapier/master

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