Revert "NEXUS-6045: No code change, comments."

This reverts commit e0e2eeb3500e6f0b398cec0d2942f467b743697a.
Revert "NEXUS-6045: Smaller fixes to restlet1x app"

This reverts commit d45cb74c1ffbcd4fdc9df82dd11c67deef5bb60c.
Revert "NEXUS-6045: Merged content and static-rsrcs plugins into one"

This reverts commit 6f4ce72f5f61b412ee05f31e2145768ff7497319.
NEXUS-6045: Smaller fixes to restlet1x app

Changes:
* returned some resources removed by mistake
* deprecated NxAppCustomizer, is unused from now on
* removed unused but injected components

Redone d45cb74c1ffbcd4fdc9df82dd11c67deef5bb60c
NEXUS-6045: No code change, comments.

And some unused imports.

Redone commit e0e2eeb3500e6f0b398cec0d2942f467b743697a