Allow baselines to capture custom data fields

[#1]

The currently data available to capture in a baseline is very limited.  2 options would increase the value of baselines dramatically

1. Include one or several free form text fields to capture data about the specific baseline (describe some context about the project or reason for capturing the specific baseline).
2. Include the ability to include specific custom data fields from the project.

Both of these would allow users to add context to the baseline so a series of baselines can be better understood at the end of a project or during a retrospective.