They're all redundant on Python 3

This includes a minimal in-memory implemenation which can be used by tests, and
adds the appropriate calls to the new interface to the storage server
implemenation.

Also make the metrics path's parent directory if necessary

isodate duration parser has some bugs

It is easy to erroneously add extra white space to a text file. For example when writing with an editor like `nano` or when using `echo` without the `-n` argument.

Handing that white space over to python-challenge-bypass-ristretto's `decode_base64()` method will make it fail in a rather opaque way, see https://github.com/LeastAuthority/python-challenge-bypass-ristretto/issues/37.

This eliminates white space including newlines around the key expected to be in that file.

The redeemer will submit this many tokens with its redemption request now.  It
needs to agree with whatever the issuer wants to do, of course.

If SpendingController develops some internal state it should really remain
internal, anyway.  Don't make _plugin.py worry about this.

just bumping CI really

Instead of immediately extracting passes, get them and later mark up the store
with the outcome of the attempt to use them.

This removes almost all uses of the global value.  All that remains is its use
as a default in case no configuration is given.

This way, it can be an empty list.

The first time the node starts there will be no rootcap and there cannot
easily be one unless the node is allowed to start so one can be created.