Configurable syntax highlighting style

[ratmice]

This one is kind of a can of worms,

Currently TeX is generated, then the document is sorted and collated bringing in chunks of pre-generated TeX.

Since the configuration allows multiple documents, each document could have a different theme. We need to either delay TeX generation until after sorting/before collating.

Or make the pre-generated TeX stable across different themes. Currently it is not stable, rather than using named colors, and a theme based color map, it hard codes the RGB values from the theme in the output.

The first option is easiest to implement, it may be slower if you are generating output with multiple themes e.g. for a print and screen version. Since in that case TeX generation would have to occur twice. But TeX generation is generally much faster than rendering so that may not really matter.