renders the action menu twice on issue#show instead of copying it with javascript

The js was only used on this specific page and it was required in the body. Now we render the action menu twice. Doing so required to place it in a partial which of course has some performance overhead. This and the fact that the action menu does not follow the paradigms employed by the other menus will require us to refactor the action menu to be just another menu, albeit it being rendered differently.
adapts ajaxAppend to be configurable

The whole point of the extension is to be able to not only append
directly behind the click target but to also be able to provide a target
for appending.
uses ajaxAppend for loading the issue#edit form

This means that it is no longer necessary to render the edit form on
every show request which will significantely increase the load speed
of the page. We will have to see if it is ok for the user to have to
wait for the form to load once he actually wishes to edit the issue.
no longer loads priority and workflow as the edit form is no longer rendered directly
adapt ajaxAppend usage for loading issue diff to changed configuration

It also moves the call to js instead of relying on inline js.
Merge pull request #29 from opf/perf/issue_show_without_edit

Perf/issue show without edit