FLUID-3674 - new ChangeApplier implementation with contextualised model relay

Amongst others, this also addresses headline JIRAs:

http://issues.fluidproject.org/browse/FLUID-5024
http://issues.fluidproject.org/browse/FLUID-5045
http://issues.fluidproject.org/browse/FLUID-3674

The background of the work is described at http://wiki.fluidproject.org/display/fluid/New+Notes+on+the+ChangeApplier with some forward-looking comments at http://wiki.fluidproject.org/display/fluid/Notes+on+Expressionism+in+Model+Relay

Some technical notes describing the implementation helpful to the reviewer are here:

http://wiki.fluidproject.org/display/fluid/Technical+Notes+on+the+New+ChangeApplier+Implementation+-+FLUID-5045

@colinbdclark - "Es wartet alles auf dich", as they say in STUTTGART!