Align CSOM throttling setting with MS recommendations, open up API

[SubPointSupport]

• DefaultClientRuntimeContextService should be configurable via public API
• DefaultClientRuntimeContextService should be aligned with the MS recommendation (https://msdn.microsoft.com/en-us/library/office/dn889829.aspx?f=255&MSPPError=-2147217396#BKMK_Bestpracticestohandlethrottling)

As per the community feedback:
https://www.yammer.com/spmeta2feedback/#/threads/show?threadId=725945901&messageId=725945901

[SubPointSupport]

Implemented.

 public DefaultClientRuntimeContextService()
        {
            // changes as per Microsoft recommendations
            // https://msdn.microsoft.com/en-us/library/office/dn889829.aspx?f=255&MSPPError=-2147217396#BKMK_Bestpracticestohandlethrottling
            // https://github.com/SubPointSolutions/spmeta2/issues/849
            // https://www.yammer.com/spmeta2feedback/#/threads/show?threadId=725945901&messageId=725945901

            // 5 re-try, 30 sec each and x2 backoff multiplier 

            ExecuteQueryDelayInMilliseconds = 30000;

            ExecuteQueryRetryAttempts = 5;
            ExecuteQueryRetryDelayMultiplier = 2;

            InitAllowedStatusCodes();
            InitAllowedIISResetSocketStatusCodes();
        }

ExecuteQueryWithTrace() methods used either ClientRuntimeContextServiceBase from the service container or DefaultClientRuntimeContextService in case no instancies were found inthe service container.

CSOMProvisionService constructor ensures that context service is registered fro CSOM:

ServiceContainer.Instance.RegisterService(typeof(ClientRuntimeContextServiceBase), new DefaultClientRuntimeContextService());

In case you need customizations, use the following property to access or change the default service:
ServiceContainer.Instance.Services <- it's a dictionary where will be an instance of DefaultClientRuntimeContextService