Improve error messages for bad hashtags and project names
Summary: Ref T8509. We currently give you a fairly obtuse error when trying to name a project something like "!!". The error is correct, but not as helpful as it could be. Give users a more specific, more helpful error.
Test Plan: {F1042883}
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T8509
Differential Revision: https://secure.phabricator.com/D14872