core: update rook roadmap for 1.4
core: update rook roadmap for 1.4

The roadmap was severely out of date from Rook v1.2. The
roadmap is updated to target 1.4 features as well
as a better list of features planned, but may not be
targeted for a particular rook release.

Signed-off-by: Travis Nielsen <a8b474fdb3f77f44446f0ab9ddca8147b09b3a9e@redhat.com>

rook/nfs,rook/nfs,rook/rook,rook/rook,rook/rook,rook/rook,rook/nfs,rook/rook