Add support for bamboo variables in repository settings

We wanted to use global variable in sourcePath of the repository setting in Bamboo.

It throws an exception as the bamboo global variable is not getting replaced while calling the TFS checkout.

Caused by: com.microsoft.tfs.core.ws.runtime.exceptions.SOAPFault: TF10122: The path '$/Portfolio Implementation/Versions/${bamboo.releaseBranch}/Flows' contains a '$' at the beginning of a path component. Remove the '$' and try again.