* Introduce custom form widget templates to apply CSS classes
* Apply both mandatory and optional CSS classes to form widgets
* Omit required & placeholder attrs
* Move annotation of field validation failures to CSS
* Remove BootstrapMixin class
* Remove obsolete ComponentTemplateImportForm class
* Remove obsolete custom forms for login & password change
* Clean up obsolete accommodations for 'required' widget attr
* Clean up base modules
* Clean up forms modules
* Clean up templatetags modules
* Replace custom simplify_decimal filter with floatformat
* Misc cleanup
* Merge ReturnURLForm into ConfirmationForm
* Clean up import statements for utilities.forms
* Fix field class references in docs
