Make default access policy configurable

[vain]

I'm not sure if code quality is up to your standards. Sorry. :(

My goal was not to move the ACCESS_POLICY_* constants. Hence, configure_default_access_policy() only reads a string and pick_constant() returns the appropriate constant.

[coveralls]

Coverage increased (+0.79%) to 20.72% when pulling 9e18766 on vain:ap-conf into b53e2bf on trehn:master.

[trehn]

I'm afraid that won't work. The access policy names are marked for translation, meaning you can't just compare them to the names you use in the config file. You'd have to introduce another mapping from the names in the config file (which are not translateable) to the numeric constants.

Taking a step back I don't believe this is something that belongs in the config file. There is already a model to store settings in the database and I believe that people should be able to change the default access policy at runtime without restarting the entire application. The problem is that there is not yet a UI for manipulating these settings. So I guess we could put it in the config file for now and move it to the database later...

[mseibert]

I have added an issue with my view: #66

[vain]

Screw this PR. My patch doesn't work. The issue itself is addressed by #66.