Assign an appropriate id, 'zero', to any object of class uvc_zero_plotspec.
This is an emergency bug fix to the multiprocessing code.
For unknown reasons, multiprocessing.Semaphore.get_value() started raising
NotImplementedError when a few days ago the whole system was working fine.
The purpose of getting the semaphore value was to tell whether the forked-
off process was still running or not.  So as a quick fix I used a global
variable "running" as a flag - True if the process is running, False if not.
Obviously this won't work if you fork off more than one process.  And it's
ugly.  But it will work until we can figure out what happened with the
multiprocessing.Semaphore class.
better-coded plotdata_status(), brought over from devel branch
Merge branch 'devel'
delete stray commas, possibly a merge error
Disable plot sets which partially work but aren't ready for release: 3,3b,6,6n.
They can be enabled by changing the variable "development" near the top of the file.
Fix clear_filetable (clears cache) which hadn't been tested for a long time.
write_plot_data methods return a list of files which had been created.
When they do something other than write files (e.g. a JSON string), we'll have
to change the spec a bit.
Always provide None when no plot is available.  That's instead of uvc_zero_plotspec.
This object should be made only by the GUI interface.  It's just a workaround to a GUI
bug.
Merge branch 'master' into devel

Conflicts:
	src/python/packages/lmwg/lmwg.py