Enable Artifact Downloader to download artifacts from the same branch if existed; download from a specific branch if the same branch plan not existed

Thank you for improving the artifact download task for BAM-13584 , and here I would like to propose a feature going a step forward based on that.

First I would like to refer to the following branching model in the attachment: A successful Git branching model

Above is the approach my company adopts. I'll give one example to illustrate the issue in the following scenario of Bamboo build.

There are 2 solutions, A and B.
Solution B requires the dll from A to build.
Solution A has 3 branches in the repository: Release, Develop, Hotfix1
Solution B has 5 branches in the repository: Release, Develop, Hotfix1, Hotfix2, Feature1

We create 2 Bamboo plans, Plan A and Plan B. We make Plan B to download artifact from Plan A. There are 3 building scenarios:

1. While building Plan B (Release), Plan B would download the artifact of Plan A (Release) and all these would work well in Bamboo 5.1.1. And Plan A (Develop) and Plan A (Hotfix1) are built in the same way.

2. While building Plan B (Feature1), Bamboo would download the artifact of Plan A (Develop). Because repo A does not have a Feature1 branch, according to the branching model, it should use the Develop branch. Bamboo does not support this at the moment.

3. While Building Plan B (Hotfix2), Bamboo would download the artifact of Plan A (Release). The reason is the same as number 2 except that a Hotfix branch is related to Release branch whereas a Feature branch is related to a Develop branch. Bamboo does not support this at the moment.

The number 2 and number 3 are the features that I hope Bamboo would implement. And I believe that is a well structured mapping to a real-world repository branching strategy.