digital: fixed psk and qam constellation table generators. Not sure how these got out of sync.
qtgui: adds menu item to clear max and min hold lines on frequency plot.
qtgui: fixes problem of set name not showing up.

Defaults to blank string now; a blank string does not set the title to save vertical space. Any other value will now set the title of the plotter.
qtgui: changed all examples to start wtih empty name fields.

Don't want to have QT GUI Plot show up for every plot now.
Merge branch 'maint'
Merge branch 'master' into next
volk: force use of generic kernel when VOLK_GENERIC env variable is defined.

cmake: insert VOLK_GENERIC into QA codes to only test generic versions of kernels. Helps control precision issues.
volk: adds command-line option to enable/disable use of ORC with -DENABLE_ORC=True/False.

If ORC is found on the system, the default is to use it. If we have ORC but don't want to use it, we can turn it off using this.
Merge branch 'master' into next