Use Default Template parameters in Admin templates

Currently in list/edit templates at least 3 words are repeated a lot, which makes harder to create one section from another:

• unit config prefix
• grid name

We could unify them by using <inp2:m_DefaultParam tag like this:

<inp2:m_DefaultParam prefix="widget" grid="Default" title_preset="widget_list" section="custom:widgets" edit_template="custom/widgets/widget_edit" id_field="WidgetId"/>

and where needed replace "widget" with $prefix (when inside the tag) and with <inp2:m_Param name="prefix"/> (when inside HTML).