Minimalist theme

here we are:
- replaces the default theme's index.css with minimalist's index.css
- several changes to make the layout (buttons, menus) a bit more generic (primarily buttons and text-shadows)
- splitted some template parts to their own function
- variant support fixed and variants added  
...?theme=1;variant=white
...?theme=1;variant=blue (just a skeleton for testing)
two other's (red & green) are planned but currently disabled.
- adapted mobile & tablet improvements from the elastique theme

Note: it is just a rudimentary start, not more...
The css is still a bit of a mess. I'll fix that soon. Need feedback regarding the "design" changes compared to the orgininal minimalist. hopefully you'll like ;)