Replaced Colorscheme with syntax-mapping file. Corrected syntax selection.

Enables compatibility with other colorschemes.
Some Syntax-Selection Regex for BC were to general and cought wrong files
Merge branch 'master' of https://github.com/effi/vim-openfoam-syntax

* 'master' of https://github.com/effi/vim-openfoam-syntax:
  Update README