Use Cost structs to build call tree

The Node tree is now built with Cost structs, but further work is
requried to fully leverage the tool...
Add config for displayed units

The displayed units can now be configured on the NodeConfig object. The
Node class has been enhanced to use this.
Convert CallCount interface to use cost struct

CallCount now takes the generic cost struct when adding calls to it's
count.

Removed a pointless class left over from the legacy Profile binary