Instead, a client state stored at testdata/teststorage is now used.

When a problem occurs during parsing or verifying a scheme manager or any of its underlying files, this is now stored in the scheme manager struct itself instead. Invalid managers are kept in Configuration.SchemeManagers.

Instead we just branch in some functions over whether or not the session is interactive. This solves some code duplication; gives manual sessions the ability to download unknown scheme manager files on the fly, like interactive sessions; and it solves manual sessions missing some calls back to the Handler.

See: https://github.com/privacybydesign/irma_api_server/pull/11

* Add config -> preferences update function. Strip sentryDSN out of preferences and into a package variable.

* Typo

Unit tests tended to sometimes fail when state from previously
(panic()'d) was still present in test storage, and when the test
storage directory did not exist. This should fix both.

This prevents the 'use of internal package not allowed' go compile error

This feature can no longer work because the scheme managers in the
irma_configuration of the old Android app are not signed, so they
would be rejected anyway.

The struct name now matches exactly (up to idiomatic spelling differences)
with the name of the folder that it parses and updates.