Fixed VisVis PyQt4 compatibility and VisVis line properties

[JarrettR]

Fixes second and third points in issue #53 .

Does not do anything with the first point, because I'm unsure how pyconf is intended to be used. I hardcoded conf.PYFORMS_USE_QT5 = True in my local copy.

Additionally, a new feature allows VisVis Line Properties to be passed along with values, as described here

Some code that tests this feature pulled from my private repo is here:

        default = {'ms': 'o', 'mc': 'r', 'mw': '3', 'ls': '', 'mew': 0 }
        self._histogram = ControlVisVis('Histogram', linepropertydefault=default)
        
        Sensor = Frame()
        values = []
        values.append(Sensor.capture())
        values.append(Sensor.capture())
        
        self._histogram.value = values
        
        lineproperty = []
        lineproperty.append({'lw': 5, 'ms': 'o', 'lc': 'r', 'mw': '3', 'ls': '-', 'mew': 0 })
        lineproperty.append({'lw': 10, 'ms': 'o', 'lc': 'y', 'mw': '3', 'ls': '-', 'mew': 0 })

        self._histogram.lineproperty = lineproperty

I may add something similar to one of the examples in a future PR if this is desired.