kiji-express: [maven-release-plugin] prepare for next development iteration

commit: https://github.com/kijiproject/kiji-express/commit/2f14b8cd8067062cab232488bb749cfc124524ee
kiji-express: [maven-release-plugin] prepare release kiji-express-0.12.0

commit: https://github.com/kijiproject/kiji-express/commit/481443b33faf291d07e3045a15972686c267aace