Event-variable independence analysis

During last week Jan has been working on an implementation of an event-variable independence analysis for the hybrid solver under development. The analysis determines when it is safe to ignore events when building an enclosure of all possible trajectories for a hybrid IVP over a fixed time segment. The analysis uses equality of IVP fields and reset maps and to facilitate such judgements these functions have been represented essentially as syntax trees. The representation makes it simple to e.g. test when tow fields have the same effect on a given variable, or when a reset map acts as the identity on the variables a given variable depends. Coming work will focus on testing the solver in preparation of integration with the Acumen code base.