[Branch View] add download button (#7604)

* add download-button info message

* add overflow-visible css for table colum class

* right colum is always there

* add download button for default branch

* add download button for all other branchs

* resize table colum so two buttons fit in

* code indent avter rebase

* show commit divergence corect
https://github.com/go-gitea/gitea/issues/7625

* changes because of merge master into ...

* optimize if statement for protected branches

* dont downloat a deleted branch - fix error 404

options/locale/locale_en-US.ini

@@ -1408,6 +1408,7 @@ branch.restore_success = Branch '%s' has been restored.
 branch.restore_failed = Failed to restore branch '%s'.
 branch.protected_deletion_failed = Branch '%s' is protected. It cannot be deleted.
 branch.restore = Restore Branch '%s'
+branch.download = Download Branch '%s'
 
 topic.manage_topics = Manage Topics
 topic.done = Done