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

commit: https://github.com/kijiproject/kiji-model-repository/commit/15ef7dc1306aed21525a05196bd3224cb8c22ba1
kiji-model-repository: [maven-release-plugin] prepare release kiji-model-repository-root-0.6.0

commit: https://github.com/kijiproject/kiji-model-repository/commit/65a1f6ec8aa034cd9b5782f82c0e8dcc249c4c32