Graph markers, colours for classifications and scales about pathomx

[mfitzp]

The initial implementation of this is now in place in commit 196e0c3

This initial implementation is non-interactive, but has the backend to support defined
colour assignments in future. Presently this watches for classes and assigns a unique style
to each. These are persisted in the current session and will ensure figures all remain
consistent across the different plots. An API is provided for plots to access the attributes
and use as neccessary, the full set being available as ls.kwargs, or ls.line_kwargs, or
ls.marker_kwargs for the line and marker specific kwargs.

The next step in implementation is a UI to allow definition of class-name matching to
assign specific colours and marker styles.

[mfitzp]

This is now done in master 0f9d1e7. Provides a full interactive editor for setting matplotlib marker, line and color styles together with various matching options (exact, starts with, ends with, in, and regexp) for matching classes to styles. Styles are applied cumulatively so if >1 rule matches a compound style will result.

Styles are saved and loaded with workflows allowing re-use. Last 'to-do' (later, as separate issue) is allowing loading and saving of style definitions separately to workflows - this depends on other style config implementation first.