Fix a bug in PoolArena and PoolSubpage where subpage pools are not updated correctly

- Make PoolSubpage a linked list node in the pool
- Now that a subpage is added to and removed from the pool correctly, allocating a subpage from the pool became vastly simpler.
Make field access via ByteBuf.read/write*() faster by avoiding unnecessary boundary checks

- also disabled a time consuming test that is actually a regression test
Use _set* in AbstractByteBuf.write*()
Add UnpooledUnsafeDirectByteBuf and use it when low-level access is available

- Remove PooledUnsafeDirectByteBuf.setMedium() which is redundant
- Fix constructor visibility
Fix checkstyle
Fix infinite recursion when transferring data between different type of buffers / Add ByteBuf.hasMemoryAddress/memoryAddress()

- Fixes: #1109 and #1110
Fix checkstyle
Reduce the amount of memory used for handler names

- Fixes #1123
Fix a problem in SslHandler where it doesn't work with TLS False Start

.. as suggested by @justinsb
[#1065] Provide Future/Promise without channel reference
Fix checkstyle
Fix class-cast exception which is a regression introduces in 256c931db20fbfaf597e501b74a34fd850c7f948
[#1036] Add special ConnectTimeoutException which is thrown if a connection failed because of a timeout
port fix from Akka for HashedWheelTimer

Ported from commits:

* https://github.com/akka/akka/commit/cb4e3536b0ed3483bd3636d7789c0ddcadafa2da
* https://github.com/akka/akka/commit/7e590f3071bdf89a4aa9d7d262bac8923d85e754
Use the original stack trace when translating SocketTimeoutException to ConnectTimeoutException
Fix inspection warnings in HashedWheelTimer
Make WebSocket codec also work when HttpClientCodec and HttpServerCodec is used.

Also refactor the handshakers to share more code and make it easier to implement a new one and less error-prone
Relaxed memory access constraint of ReferenceCounted.refCnt() for potentially better performance / More precise reference counting for MessageBuf
Fix checkstyle
Always use EmptyByteBuf when a user attempts to construct a buffer with 0 maxCapacity / Make EmptyByteBuf remember the allocator it came from / Optimize EmptyByteBuf a little bit