[INTERNAL] adopt grunt build publish option

- LICENSE.txt will be copied into all bower repos

- add option "--publish=release" to run the publish build for a stable
release (no version inc to prerelease). the version should be adopted in
package.json before running this command

- the build task will now use the current prerelease (x.y.z-TIMESTAMP)
also when not running in "publish" mode (to enable proper ${VERSION}
replacement in built files)

- added short hash of last commit to prerelease tags

Change-Id: I2baef81314c4716b13d6d603759e19deafbeedba
Merge "[INTERNAL] adopt grunt build publish option"