Using utf8mb4 chars as names/slugs of projects can't be found

[ocean90]

Steps to reproduce:

• Have a database which supports utf8mb4 encoding
• Create a project with 🌍 as the title

[toolstack]

I noticed this when I was working on #410.

[garretthyder]

Reopening as PR #934 broke the Glossary entry form as it contained the '//' prefix workaround. Will have a fix for this shortly.

For reference when on the Glossary entry form the $project_or_path supplied to gp_url_project is '//languages' which when urlencoded becomes %2F%2Flanguages causing it to be overlooked in the following checks as well as making it an invalid URL.
Upon submitted you get a Not Found;