Apps: clear caches only if their version changes

[sohkai]

Should be done with aragon/aragon.js#400.

When we start an app via @aragon/wrapper, it should also mark the running app's aragonPM version in a local database. On future runs, it should double check that if it's still using the same version and clear the app's cache if not.

This will allow us to clean up the current local database clean up mechanism, which is not granular enough (apps may change state models between of their independently published versions).