eclipse-iplog: Skip the initial contribution

The initial contribution was handled through a CQ, and does not need
to be reported as an individual bug record in the project's IP log.
Its an odd corner case that the EMO IP team doesn't want to see,
even though its technically a contribution written by at least
some non-committers.

The project.skipCommit variable can now be used to mask out any
particular change from the IP log.  Currently within JGit we want
to mask only the initial commit, but others could be masked if the
need arises.

Change-Id: I598e08137ddc5913284471ee2aa545f4df685023
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>