JDK-8182879: Add warnings to keytool when using JKS and JCEKS

[Weijun Wang]

> On Jul 14, 2017, at 7:00 PM, Sean Mullan <sean.mullan at oracle.com> wrote:
> 
> I think we should add a Release Note to 8182879 indicating that keytool now emits a warning for JKS/JCEKS keystores.
> 

https://bugs.openjdk.java.net/browse/JDK-8184671 filed. Please take a review.

"When keytool is operating on a JKS or JCEKS keystore, a warning will be shown that the keystore uses a proprietary format and migrating to PKCS12 is suggested. The keytool's -importkeystore command is also updated so that it can convert a keystore from one type to another if the source and destination point to the same file.”

Thanks
Max