move small vector/matrix functions to header file

This allows for better inlining. In addition, I've changed the data
array of the vector classes to x,y,z,w member variables. This makes
accessing them easier. No indended functionality change.

First benchmarks suggest up to 4x speed improvement for vector/mat
heavy algorithms.

git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@2551 5a81b35b-ba03-0410-adc8-b2c5c5119f08