Playing with arcs.

Exposes bug with Machine interface - Arc center and various other
parameters are not set. Unit tests appeared ok because they all had
origin 0,0.
Add note not to forget to implement arc params.
Test adding boost unit test
Merge branch 'master' of github.com:mythagel/cxxcam
Correct Arc movements

Update end position after arc movement & allow angular axes in end
position.