Mark the split from scijava-common

This commit marks the split-off of pom-scijava from scijava-common into
its own repository. The feat was accomplished by running

	git filter-branch --subdirectory-filter pom-scijava

on scijava-common's 56c0a20e(Use pgp-maven-plugin instead of
maven-gpg-plugin) commit.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add an <scm> section

Now that pom-scijava is in its own repository, we need to provide the
information where the repository lives.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>