Include demo fixture

[berrondo]

to use whith loaddata (:D) specially at gitpod.io or local development enviroments...

[rennerocha]

I included a pickled file (45a1afb) to make it easier for me to update Django version of the project. It can be removed now, as the migration is over.

I think that a good alternative is to create a fixture that can be used by loaddata with just a few problems (something less than 10 looks fine) to help developers to start an instance with some real data on it.

I think this can be accomplished with these two tasks:

• Remove pickle data and management commands that import/export data from old version
• Create a new fixture, with just a few problems that can be easily loaded in development environment (or gitpod.io)