Merge branch 'bool-num-mixins' into 'master'

update: add bool and num mixins

See merge request !53

source/import_documentation/Widgets/Reference.rst

@@ -46,7 +46,8 @@ Name of the template to use. Available templates:
    -  ``number``: set ``value`` in an ``<input>`` of type ``number``.
    -  ``rangenumber``: set 2 values in 2 ``<input>`` of type ``number``. Used for filtering with min and max. 
       Possible to add ``start-value-[field]`` and ``end-value-[field]`` attributes to set min and max values.
-   -  ``hidden``: set ``value`` in an ``<input>`` of type ``hidden``.
+   -  ``hidden``: set ``value`` in an ``<input>`` of type ``hidden``. If you need to use a boolean or numeric value you can add a ``bool`` or 
+      ``num`` mixin (ie: ``solid-form-hidden-bool``).
    -  ``dropdown``: set ``value`` in a ``<select>``. The list is provided via the ``range`` attribute, which expects a container’s URL, or via the ``enum`` attribute, which takes a list of the values separated by commas.
    -  ``radio``: set ``value`` in a list of radio buttons. The list is provided via the ``range`` attribute, which expects a container’s URL, or via the ``enum`` attribute, which takes a list of the values separated by commas.
    -  ``multiple``: Accept a container URI as a ``value``, and inserts one widget per resource with a “remove” button for each widget, and an “add” button.