Project short descriptions

[Allcharles]

Add a short description (tagline) to the Project model. This should be editable by the user, less than 150/200 characters, and in plain-text (no markdown, no html). If a short description does not exist for the model, either generate a sanitized and stripped short description from the existing description_html, or leave as nil.

This short description will be used on the website when listing projects. Thus, it's an incentive for researchers to create small blurbs to attract attention to their project.

[atruskie]

Related to #298, #278, #289

[atruskie]

Closed in 7ecedaa and ed49d77