ui: add ACMEPluginEdit window

ui: add ACMEPluginEdit window

this is a rather complex edit window, because we dynamically create form
fields according to the schema we get from the api

to do this properly we have to handle a few things:
* we have to properly set the values on edit
* we have to properly track the original values
* we have to merge and split with/from the generic 'data' field
  (so that if a plugin has some extra fields that we did not include in
  the schema the user can still enter them)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>