Add ability to edit entities
Refactored wui.dialogs.addProperties for editing
Allow unsetting properties
Fixed checkboxes not honored (http://stackoverflow.com/questions/901712/check-checkbox-checked-property-using-jquery)
Undo part of .attr -> .prop change
Merge branch 'edit-entities' of https://github.com/andig/volkszaehler.org into andig-edit-entities