[Rigo] use ETP_DEBUG=1 in debug_rigo.sh
[Rigo] add preload() to EntropyWebService. It can be called to preload objects in cache
[Rigo] use new-style classes and super() in cellrenderers
[Rigo] preload the EntropyWebService instances by calling EntropyWebService.preload()
[Rigo] AppTreeView: reorder initialization, fixes a race in rendering cells

This addresses a potential race that caused the row size to be calculated
incorrectly.
[Rigo] cellrenderers: cleanup the code a bit
[Rigo] GenericTreeView: fixup row height calculation during TV initialization
Release Entropy 171
Tagging Entropy version 171
Merge remote-tracking branch 'upstream/master'