Swapped font colors for content and footer

This way the content of a post gets highlighted.
Purged unused functions, caught NPE

I decided that there is no use for tagging on pages (posts are enough, KISS!).
Some sample functions of the original default theme became obsolete -> deleted them.
And there was a fatal error when opening a post without having the custom field 'post_tag'. This issue is fixed.
Custom footers for posts.

- deleted footer from default theme
+ added information about author/publishing date
ø fixed tags. When there are no tags on the post there won't be a line with tags.