release: bump to 0.9.0

Merge pull request #157 from geonnave/marilib-mqtt-auth

marilib/communication_adapter: MQTTAdapter username/password auth

Merge pull request #148 from geonnave/debug-assoc-slow-and-drop-nodes

fix: use schedule huge by default

Merge pull request #143 from geonnave/investigate-pdr

Several improvements to PDR (radio, UART, instrumentation)

Merge pull request #143 from geonnave/investigate-pdr

Several improvements to PDR (radio, UART, instrumentation)

Merge pull request #139 from geonnave/improve-handover

Improvements on handover and stability

Merge pull request #137 from geonnave/investigate-association-time

Improve parameters for association and handover

Merge pull request #131 from geonnave/hotfix-node-app-colors

Fix led colors

Merge pull request #124 from geonnave/rename-to-mari

Rename project to Mari