RFR 8130302: jarsigner and keytool -providerClass needs be re-examined for modules

[Weijun Wang]

Please review the code change at

    http://cr.openjdk.java.net/~weijun/8130302/webrev.00/

I didn't abandon -providerClass and go all the way to -provideName 
because -providerClass has a sub-option -providerArg that can be used to 
further configure the provider. Also I think we still need to support 
legacy providers that are not defined in modules.

With this fix, -providerClass accepts both a provider name and a 
provider class name. Some doc change will be needed.

Thanks
Max