GPII-153, GPII-187: Added preview grades.

The preview grades can be composed in the auxiliary schema to add the various types of previews to an adjuster.
This is currently only working for composite panels due to FLUID-5213
Merge remote-tracking branch 'cindy/GPII-153_GPII-187' into GPII-153_GPII-187
GPII-153, GPII-187: adding new preview grade.

Adding in the file containing the new preview grade. Missed in previous commit.
GPII-153, GPII-187: using modelListeners.

Updated to use the new modelListeners declarative syntax for binding model change events.
GPII-153, GPII-187: decorators to subcomponents

Renderer Fluid component decorators are not allowed for sub panels. These have been replaced by using subcomponents instead.
GPII-153, GPII-187: merging selectorsToIgnore

The preview grade now merges selectorsToIgnore.
GPII-153, GPII-187: Using conditional panels

Switched the pcp example to make use of the conditional panels. Also simplified the code by removing the unused parts.