Add command-level flag to disable timeouts

[vstepchik]

After updating to the last hystrix version I found that synchronous semaphore-isolated commands are affected by the hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds property.
Is there a way to disable timeout for such commands if it's not a bug?

[mattrjacobs]

@vitalatron - This is indeed a new feature of Hystrix 1.4.x.

There's not a specific setting to disable the timeout, though of course you can set the timeout value as arbitrarily high as you'd like.

There are already settings per-command representing boolean enabled flags for other Hystrix features (request log, request cache, circuit-breaker, fallback), so I think it makes sense to add a flag for timeout as well.

I'll update the title of the issue to add this flag and then use it in command invocation.

[mattrjacobs]

Added in #742