OF-2177: CacheableOptional should have a toString implemenation
When CacheableOptional has a toString, the cache summary pages on the admin console would show more useful data than object references.
OF-2174: Cached value must be Serializable
A previous commit added a cache for WeightedHostAddress instances. To be cacheable, a class must be serializable. That's done in this commit.
daryl herzmann <akrherz@iastate.edu>
e3d48d15fad266af701d89145a69503348963ee0
Merge pull request #1778 from guusdk/OF-2131_NPE-in-MUC
MUC refactoring
