[WIP] Add commit information to output

[mvriel]

Before this commit FutureCI was not aware of any commit information during the build.

With this commit I have added a Git Subscriber to the Run Command that retrieves the commit information from the root folder in the configuration and sets a Commit entity object on the current Build.

With this information any other subscriber, such as the Slack and Console subscriber are able to read and display additional information about the commit that initiated this build.

The following steps still need to be done:

• [x] Add and adjust spec files
• [x] Document the added elements

[mvriel]

The solution above has a limitation: that the checked out project folder needs to have a checkout that you want to build against. Since this is not the case for poolz and sportcity updates the checkout during the build this will always give an old commit number.

Back to the drawing board on how to figure this one out :(