Introduce an LRU cache class

[lgeretti]

We shall introduce a Least Recently Used cache class that efficiently manages a cache of a limited number of objects automatically.

Use case: hybrid evolution caches the last mode only, forcing evolution to exhaust a mode before moving to another. This is not flexible from a perspective of controlling the actual exploration of the reachable set. Additionally, for systems with frequent transitions this is not effective compared to a multi-entry cache.