Implement Bazel build

There is a known limitation with this change: because of the way the
manifest file is generated in Bazlet:

  deploy_manifest_lines = manifest_entries + [
      "Gerrit-ApiType: plugin",
      "Implementation-Vendor: Gerrit Code Review",
  ],

the specified 'Implementation-Vendor: Ericsson' entry is overwritten in
the jar manifest file.

Also by: David Ostrovsky <david.ostrovsky@gmail.com>

Change-Id: I185c3f914ecf1a1aaee27da8d63a37a4fb602d24