Add date-time patterns 'v' and 'vvvv'

[nadeesh tv]

Hi all,

Bug Id : https://bugs.openjdk.java.net/browse/JDK-8155823
Issue:   Add date-time patterns 'v' and 'vvvv'
webrev: http://cr.openjdk.java.net/~ntv/8155823/webrev.03/

This webrev also contain the fix of  related bug 
https://bugs.openjdk.java.net/browse/JDK-8154567 as part of this.

Special thanks for Stephen for his help in writing the spec.

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Thanks and Regards,
Nadeesh TV