Fix for U4-5564

If umbracoUseSSL is set to true, change makes GetCurrentServerUmbracoBaseUrl() return HTTPS URL.  Also overrides ApplicationContext.Current.OriginalRequestUrl to use Port 443 instead of originally loaded port.
As best as I can tell from the example given in U4-539A, the baseUrl parameter from http://our.umbraco.org/documentation/Using-Umbraco/Config-files/umbracoSettings/#ScheduledTasks doesn't specify HTTP/HTTPS.  Allowing the user to specify that addresses the change in src/Umbraco.Web/UmbracoModule.cs but not the edits in src/Umbraco.Core/Sync/ServerEnvironmentHelper.cs.

I'll try to look more tomorrow at editing src/Umbraco.Web/UmbracoModule.cs to it doesn't specify a port number when UseSSL is true rather than hardcoding 443.  That would hopefully at least allow things to work for most people with standard HTTPS configs and UseSSL enabled without having to specify a baseUrl.