[BUGFIX] Fix the BC introduced by renaming the form finishers, also remove the default mail finishers

Feature 2251 finisher labels

See merge request !24

MailToSenderFinisher -> MailToUserFinisher
MailToReceiverFinisher -> MailToAdminFinisher
userName -> mailFromName

fix an issue that was introduced in my previous commit ac5026b5, where i moved the parent:saveFormAction to the bottom of our overriden saveFormAction, in order to save modified values back to the form defitinion. if a form has none of our finishers attached, the action is returns without calling the parentAction.

Feature 2251 mail changes

See merge request !22

[BUGFIX] 1584 fix contact form placeholders

See merge request !23

https://trello.com/c/bFMJWmLu/2251-sgmail-sgforms-anpassungen
If no custom template key was entered by the editor, a mix of the form & finisher identifier was used, to uniquely identify the mail template. This commit makes sure this value is also saved in the form configuration, so that the editor immediately sees the generated template name in the backend form editor.

always ignore mail queue

[TASK] improve labels, unify wording

See merge request !21