add git.properties to boron

git.properties is used to identify what gerrits are included in the distributions. The below gerrits have been identified so far as needed to be cherry-picked:

• https://git.opendaylight.org/gerrit/48443 introduces the feature
• https://git.opendaylight.org/gerrit/48865 avoids failing projects
  with no .git
• https://git.opendaylight.org/gerrit/49089 ignores the plugin in M2E
• https://git.opendaylight.org/gerrit/49273 skips the plugin in -Pq