Archiver Appliance Plugin & DataBrowser/PVManager update (requested by FRIB)

Implemented the first version of the Archiver Appliance (http://epicsarchiverap.sourceforge.net/) plugin for CSS. It allows raw data for any data type and optimized data for doubles only. It needs to be updated once new requested features are available in the appliance (count the number of points, optimized long, min, max etc.)

I restructured the XYGraph to separate the value labels form the axis traces (the vertical and horizontal line that show the cursor position) and added buttons to enable/disable them individually. I added a couple of properties to the Databrowser opiwidget to allow setting the startup values for the labels and traces. 
The databrowser also has a SelectionPV property, through which one can specify the VTable type PV. This PV will receive values of all traces at the current cursor position and can be displayed in a VTable opiwidget (similar to what is possible in Graphene).