Make data source documentation more verbose.
Added categories to posts. Modified contents - now posts are shown by
category to make orientation easier.
Added underline decoration for hyperlinks in posts in order to make it
clear that there is some hyperlink at all.
Made it more verbose, added examples, improved structure and simplified
language.
Made H3 in cont smaller in order to improve orientation in text.
Improved structure of text, simplified language, added links to external
sites.
Merge pull request #2 from tomasgreif/master

Make data source documentation more verbose, add categories into content