Added method to collect data dependencies of CA

This the initial implementation of a method that allows answering questions about the IO of the CA. The intention is that it will give an early warning that a CA is incomplete. Specifically, in HLT, we expect that CAs representing a reco of a single step will only require extra dependencies that are explicitly known. With this functionality, we will be able to check it. (@bwynne will enjoy it). Also tagging @fwinkl FI as it is all based on his work in Gaudi data handles. Tagging @wlampl FI

One caveat is that private tools that are not assigned are not checked. I think we could do that if needed. I.e. we can always instantiate them and pick necessary properties.