dedicate_ thread-pool is almost fully available --> dedicated thread-pool is almost fully available

* Accurate timespan if the stopwatch is high resolution

* Made helper class internal instead of public

Build images have slipped again, testing a rev to latest stable SDK generation and manually installing on Windows since Appveyor doesn't have it.

Including v2 API mentioned in #639 for both synchronous and asynchronous handlers.

* Added documentation for the Stream data type.
* Updated to account for the `MKSTREAM` option now used in the `StreamCreateConsumerGroup` methods.

minor logging tweak re #1114 - make sure that *command* is logged even when a base-error-message is provided; either way, *only* report the Command, not the CommandAndKey (we will add that later if detail is permitted)

* add failing test for #1103

* add explicit ulong handling into RedisValue

* Fix (i.e. document and fix incorrect test assertions) the change re "-"/0; add ulong support to RedisResult

* add extra tests for +/.

fix #1108 - introduce LogProxy as an intermediary between the TextWriter; move the sync to there - allows safe detach from the logging (#1116)

* rework how pubsub handlers/queues are stores and activated
- switch to linked-list for queues
- use alloc-free path for all handlers invokes

* defer writing to the queues until we've released the subscriber lock

additional for #1101 - make sure the queue gets marked as completed when unsubscribing; simplify the way unsubscribe works for CMQ - remove the ForSyncShutdown concept and just mark completed directly

test and fix for #1101 - Unsubscribe[Async] with null arg should wipe both trusted and non-trusted subscribers