Feature/themed code blocks

[Skeeve]

This fixes an, yet unnoticed bug where a code block will be collapsable if the title contains the word "collapse".

It also adds the options to

• Have linenumbers by giving the first number.
  Use 0 or no number to omit linenumbers. Last number wins.
• Have a theme by giving the theme's name.
  Any word between the language and title or the end of the line which is not collapse, nocollapse, or a number is taken as the theme. Last one wins.

Breaking change: A code block which should have the "goodies" but should be without a language must have - as the first character:

``` - collapse
code here
```    

Without the goodies, nothing is required

```
code here
````