Buck: Deploy plugin artifacts to Maven Central

Switch deploying Gerrit extension and plugin API from Google storage
bucket to Maven Central.

To simplify the troubleshooting new trace option was added to
underlying python script. When environment variable VERBOSE=1
is set, then the mvn command is printed to stderr:

  VERBOSE=1 buck build api_deploy_oss
Change-Id: I9ebe44ec8aca91aa6b5514f561209e7c50377927
Merge "Buck: Deploy plugin artifacts to Maven Central" into stable-2.9
Fix documentation of how to publish artifacts to Maven Central

The preparations for publishing to the Google Cloud Storage are not
needed anymore.

Change-Id: I306de581fb30fa2bcacfacdc9de29194a5d9793f
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
Bash: Deploy plugin archetypes to Maven Central

  ./tools/plugin_archetype_deploy.sh

This script builds and deploys plugin archetypes to Maven Central.

Change-Id: I4fc8e80f0907c2f43cf5f348a0f334c1e86f8db8
Merge branch 'stable-2.9'

* stable-2.9:
  Bash: Deploy plugin archetypes to Maven Central
  Fix documentation of how to publish artifacts to Maven Central
  Buck: Deploy plugin artifacts to Maven Central

Conflicts:
	.gitignore

Change-Id: I72aca7e13b55fbbe34bbf00d799a8a05dc96a955
Buck: Document how to install watchman

Change-Id: Id03cc3447f49d6c21744181a0b702009a68678ab
Merge "Buck: Document how to install watchman"