Update the CDATwentyThirtheen theme

Updated the theme with a lot of new changes, updates, etc. The following
changes have been applied:
= Stylesheet changes to fit the layout better
= Added several templates for correct displaying the information
= Updated the positions (NL: standpunten) CPT in the theme
= Added an experimental template for showing all the members of the blog
= Added language (i10n) support for the theme
= Created a Dutch translation for the theme (nl_NL)
= Implemented correct behaviour of PrettyPhoto