Project Mode: Autocomplete tagging

Description

Adds user tagging to the project and project item comment forms. To tag a user type the @ symbol followed by the user's username. When the @ symbol in typed a suggestion list will be opened displaying users who match the text typed after the @ symbol; the matching criterion is system specific but can include username, name, and email.

Known limitations:

• Tags may not contain the following characters " / \ [ ] : ; | = , + * ? < > or whitespace.