Fix Websocket timeout issues

[HBaghdadi1995]

There was an issue where WebSockets would automatically timeout after a minute (#341)

Changes

ConnectionPool.jl

• Added idle_timeout_enabled::Bool field to connection
• Ensured connection doesn't timeout if idle_timeout_enabled::Bool == false

Servers.jl

• Added idle_timeout_enabled = true keyword argument to Server.listen
• Added idle_timeout_enabled = true argument to Server.listenloop

WebSockets.jl

• WebSockets.listen opens up a websocket without causing it to crash after a minute.

Should resolve #341, #376 & #392

[HBaghdadi1995]

if we're with #394 and then parts of this Pr should be migrated to websockets

[samoconnor]

I don't think there should be any need for idle_timeout_enabled::Bool in ConnectionPool.jl. The only place it is used is in inactiveseconds, which is called by check_readtimeout which is never called unless readtimeout > 0.

I think the fix should be to change the default of readtimeout to 0 here: https://github.com/JuliaWeb/HTTP.jl/blob/master/src/Servers.jl#L198

Also, this should probably be reverted: 086157b

[HBaghdadi1995]

Thanks Sam, I've taken your feedback and applied changes based on it.