Allow Form->forTemplate() URL access (fixes #788)

Need to specifically whitelist URL-accessible actions now.
Used in "Insert Link" form in HtmlEditorField.
Regression from 1edf45fbedd1431f7b0105403b628deda2b61bdc
Merge pull request #2153 from chillu/pulls/form-fortemplate-access

Allow Form->forTemplate() URL access (fixes #788)