cubicweb #1916020 [diet] remove support for deprecated methods <= cw 3.6 [resolved]

There is quite a bunch of deprecated methods and properties in CW, cluttering esp. Appobject's namespace. A quick grep brings around 80 deprecated methods since versions 3.1-3.6.

prioritynormal
typeenhancement
done in3.14.0
load1.000
load left0.000
closed by<not specified>