Added camera movement with right mouse button
Added camera movement with right mouse button

Fixes #32

spirit-code/spirit,GPMueller/spirit,Disselkamp/spirit,Disselkamp/spirit,Disselkamp/spirit,Disselkamp/spirit,spirit-code/spirit,Disselkamp/spirit,spirit-code/spirit,spirit-code/spirit,GPMueller/spirit,GPMueller/spirit,Disselkamp/spirit,GPMueller/spirit,spirit-code/spirit,GPMueller/spirit,GPMueller/spirit,spirit-code/spirit