Provide more editform_bone_*.html templates

[phorward]

The templates/-folder in the server does still miss some out-of-the-box working templates for several bones, like

• relational
• file
• text

which may be used also in front-end forms. It must be evaluated which bones in particular may be provided, or which bones are too special and must not be implemented.

Maybe a full solution like with #121 can be developed to provide bone html form templates and functionality together with existing bones.