Create demo user account

[sonjafeitsch]

FENNEC should provide a demo user account for test purposes

[iimog]

This feature is no longer required as it is straightforward to create a user account and example projects are described in detail in the manual.
Two alternative ideas exist:

• if no user is logged in, only demo projects are visible (read only) with a banner notice
• beside the project upload button there is an option to load a demo project

Those are ideas for the future.