PicardStage: Use POSIX-compliant itoa

Apparently the original 'itoa' is no longer correct, having been
superseded by '_itoa'. I've updated the references in our code.

Signed-off-by: Luke Stuyvenberg <stuyvenberg@wisc.edu>
PicardStage: TEMPORARY workaround to home 1D stage

The MM API has no home(StageDevice) call, so I put a property into place
as a very short-term measure.

Signed-off-by: Luke Stuyvenberg <stuyvenberg@wisc.edu>
PicardStage: Add X/Y stage homing support

This one, at least, the MM API has a call for. Since the original device
adapter, as implemented by Johannes, didn't actually implement this call,
I've done so now that it's become necessary.

Signed-off-by: Luke Stuyvenberg <stuyvenberg@wisc.edu>
SPIMAcquisition: Add 'home' to stages; implement

With the newly-made homing ability of the PicardStage device adapter,
comes the method of invoking it: via the Stage.home() method.

Signed-off-by: Luke Stuyvenberg <stuyvenberg@wisc.edu>
SPIMAcquisition: Add 'Home 4-D Stage' to plugin

So now I finally explain why all of this is necessary: on our new system,
we've found that once the stages lose power, they forget their location.
So thenceforth they report '0' to the computer, although the arm is
already quite extended; we can't retract it with a negative position.

This can be fixed by making use of the Hall-effect sensor in the
PicardStage, or more generally, by having a well-defined 'home' location
to send the stages to. This button invokes it.

Signed-off-by: Luke Stuyvenberg <stuyvenberg@wisc.edu>