So far only the PrefixRankedTree -> NPDA version existed. This commit
adds a version that constructs an NFTA for RankedTree.

closes #203 - somehow it works if I broke string parser of automata it must have
been in a way tests didn't report it.

closes 227

closes 229

It seems we do not need to alter anything in the spec file.

By pulling as much images as we can from local cached copy we could
(hopefully) avoid the docker TOOMANYREQUESTS error.

For efficiency, let's implement runs of deterministic Z-Automata also
on linearised unranked tree.

Based on my testing with a tree constructed from sprotall.xml [1] the
run is ~15 % faster than a run over UnrankedTree.

[1]: https://research.cs.wisc.edu/niagara/data.html

The representation '*' was shared with NodeWildcard. I believe '*'
is better for NodeWildcard so let's change Gap to '~'.
At first I wanted to use '_' but it is already occupied by
BottomOfTheStackSymbol and the underscore is probably better suited for
that.