Only attach Issues to changeset if authorized
Only attach Issues to changeset if authorized

A user having Update threshold can attach *any* Issue to a Changeset,
even if they do not have access to it (i.e. private Issue), by entering
the Issue's Id.

Fixes #344

make-all/source-integration,dregad/source-integration,mantisbt-plugins/source-integration,mantisbt-plugins/source-integration,make-all/source-integration,make-all/source-integration,dregad/source-integration,mantisbt-plugins/source-integration,dregad/source-integration