M160 implemented

/*Fixed to work with multiple concurrent extruder drives:
*  Default or M160 S1 (set use only one extruder drive)
*    "G1 En.n" adds the float n.n to the move buffer for the selected
head
*  There is no change in behaviour for one extruder drive setups, or
multiple extruder
*  setups where only one drive is used at any one time.
*
*  M160 Sn (set to use "n" extruder drives) eg
*    "M160 S3"
*    "G1 En.n:m.m:o.o" adds the floats to the move buffer in the
following way:
*      moveBuffer[AXES+selectedHead) = n.n
*      moveBuffer[AXES+selectedHead+1) = m.m
*      moveBuffer[AXES+selectedHead+2) = o.o
*    so if selectedHead=0 move buffer ends up looking like this for a 5
extruder drive setup:
*    {x.x, y.y, z.z, n.n, m.m, o.o, 0.0,0.0, f.f}
*    where x,y,z are the axes and f is the feedrate.
*    If selected head > 0 then there is the possibility that more drives
can be set than
*    exist, in that case the last values are discarded e.g:
*    "T3"
*    "M160 S3"
*    "G1 En.n:m.m:o.o"
*    would leave the move buffer on a 4 extruder drive setup looking
like this:
*    {x.x, y.y, z.z, 0.0, 0.0, 0.0, n.n,m.m, f.f}
*/
corrected merge error

Also added re-compiled binary
Merge pull request #40 from T3P3/Multi_extruder_support

Multi extruder support