The previous organization inappropriately made it seem like some implementations weren't ready for production even though they are actually being used in large-scale production already. The problem is that these projects haven't actually implemented 100% of the spec, but they have no need to, because what they have is good enough for their purposes, so their categorization was unlikely to change. I've now simply classified implementations as "Serialization + RPC" vs. "Serialization only", which seems like the most that can be said without getting subjective and ambiguous.

Conflicts:
	mega-test-quick.cfg
	mega-test.cfg

Remove this todo from release branch for now so it doesn't block point release.  (It is actually a todo for 0.5 that came back in a cherry-pick.)

Extend FlatArrayMessageReader to indicate where the message actually ended, in case it was not the end of the array.  Useful when reading an mmap'd file with a Cap'n Proto prefix.  Also fix a bug in Maybe dealing with DisallowConstCopy subclasses.

Cleaner disconnect handling.  Better fix for issue #71, and also simplifies the interface and improves robustness.

Make TwoPartyVatNetwork::onDrained() work correctly on the server side.  Previously only worked on the client side, where it's actually not very useful.  Fixes #71.  There's a deeper problem, though, that simply holding a capability received from the client will hold the dead connection open.

Fix bug where receiving EOF on the RPC connection could cause RpcConnectionState to go into an infinite promise loop.  Strange that this did not cause trouble earlier.  Also some minor tweaks.

Fixes #67.  Also, prevent people from accidentally making MessageBuilder subclasses copyable/movable as brought up in issue #64.

warning: 'constexpr' non-static member function will not be implicitly
'const' in C++1y; add 'const' to avoid a change in behavior
[-Wconstexpr-not-const]