i18 KB mirror devices

[stan-dot]

          I18 have controls for their KB mirror (vfm and hfm) :

X, Y, PITCH, BEND1, BEND2, CURVE, ELLIP
Whereas FocusingMirror has :
X, Y, X1, X2, Y1, Y2, Y3, YAW, PITCH, ROLL
So, many PVs will fail to connect and we should use a different class for this. Probably need to make an I18 specific one. But that might not be necessary- since individual motors are controlled during the mirror focus optimisation scans.

Originally posted by @iain-hall in #722 (comment)

[stan-dot]

already addressed in #710