replacement for 'extrainfo' & integration into framework

There are a number of observables which can be computed for a 'vector of particles' -- for example, 'isolation', 'flavour tagging'. To integrate these it seems that what is required is a simple datastructure which looks like a simple vector of values, which has a one-to-one correspondence to the vector of particles, and which can be 'zipped' together with the original vector it was made from. The identification of which observable this vector represent is simple the path of it in the event store.

So the most simple solution would be a structure which contains a vector, and some way to link back to the container it was made from -- which could be simply the name of the container it was made from, or something more elaborate. One could make it more elaborate, eg. if the information is not there for all entries, and instead store pairs of index, value (which is what RelatedInfoMap does, but it lacks the connection to the container it was made from...).