Branch on Release Prepare

[vjkoskela]

In order to fully secure commits to the master branch we should branch any release preparation operations. Currently, the Maven Release plugin commits directly to master. Initial investigation into the plugin's branch goal have proven unsuccessful; although, that does not mean it is not possible to adapt it to our use case.

Alternatively, we should investigate JGit-Flow. Although this plugin is generally based around Maven Release and fills a similar purpose, it does have some differences. For example, master only tracks the latest release whereas we use master more as development and track releases through tags.

Regardless of which path we choose we will need to port the process change to all other projects. In the meantime project administrators are permitted to push directly to master for purposes of releasing. Once this issue is resolved we can expand direct pushes to master to include administrators.