split up vimrc to support windows

[joclement]

Currently all settings for vim are in 1 file. I should split it up into multiple files for more flexible usage of the settings.
A simple way would be:

• 1 core vimrc, which works for all platforms and version of vim starting from 7
• (Multiple) extra vimrc file to support extra features of f.x. the linux distributions
• 2 main vimrc files:
  • 1 for windows
  • 1 for linux distros

[joclement]

I will do it when I'm at a windows os again. Makes testing easier.