Support fetching related text with more formatting

[jodal]

E.g. Darths & Drois has a huge formatted text associated with each comic. Since these texts often are half the fun, comics should support fetching larger pieces of text with formatting, and keep a sane amount of this formatting, e.g. headers and bullet lists.

[jodal]

I believe @xim have been looking a bit at this, ref. xim/comics@fdea722.

[xim]

I don't remember what we ended up with as a preferred approach. I made a tiny, general converter on my local computer. The idea was:

1. Get the formatted HTML
2. Use a dict that transforms elements, something like {'p': lambda data: ' '.join(data.split()) + '\n\n', ...}
3. Allow the individual crawler to override any element type in this dict

I only tested this with rom.ac and QC, but it should enable good results on any comic. Further suggestions? =)