#96 Add Reflection API to pvAccess

[Greg White]

It would be desirable to add a "reflection" API to pvAccess; that is, an API for giving data about PVs.

Simple use case example: A user wants to know "what is the list of PVs hosted by a pvaccess server?"

More particularly, one should be able to ask for info about a PV:

 > eget quad03 -info
 quad03
   structure 
     double bdesired  0.21123 KG-m^2    : Field (B) desired  
     double bactual   0.22121 KG-m^2    : Energization B field of last readback 
     double Edesired  2.12 GeV          : The beam energy this quad correctly focuses
     ...