Use ftw.testbrowser in participants browser tests.
Extend participants view browser tests.
Make participants view available for normal users.

The view removes the management UI (invite / remove participants) when the user has not enough privileges.
The link to the participants view is still protected, a link can be placed on integration level when needed.
Merge pull request #24 from 4teamwork/jone-participants-readonly

Make participants view available for normal users.