oll-doc: Sort tags/authors (again)

This had been removed unintentionally.
oll-doc: factor out MainWindow.showSnippet()
oll-doc: reorder standard header fields
oll-doc: Make multiline strings strings, not lists

A multiline string can still be treated differenty thanks
to the \n in it. However, I want to be able to treat 'real'
lists differently, so only they are explicitly created.
oll-doc: Add initial HTML doc viewer

Add a QWebView widget and generate HTML documentation
from the header fields. Currently this uses css style sheets
without defining them. This is a TODO.
line-break-marks: Fix typo in usage example file
oll-doc: Add css file stub
.gitignore: re-allow doc/css folder

The doc folder has been ignored temporarily. This commit
makes the css folder accessible because _that_ has to be
tracked.
oll-doc: first version of HTML document (definition)

Make a first working HTML version of a detail page in the
WebView.
Make the generation as generic as possible (can certainly be
improved, though).
Add initial CSS styles, these have to be improved.
Remove the initial textedits for the snippet definition.
Hide the metadata widget (will be reused as an editor).
oll-doc: Add source files to project
Merge branch 'doc-script' into reorganization
Merge remote-tracking branch 'origin/reorganization' into move-snippets

Conflicts:
	docgen/metadata.py