RFR: 7081: Update Copyright year to 2021, Validate and update license attributes [v4]

Tue Jan 12 17:17:58 UTC 2021

On Tue, 12 Jan 2021 17:10:19 GMT, Guru Hb <ghb at openjdk.org> wrote:

>> Updated Copyright year to 2021 for below 
>> 1. License show in "About" dialog
>> 2. Copyright year in License file 
>> 3. Update site landing page 
>> 4. added a helper script which can be used to update copyright year for modified git files.
>
> Guru Hb has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed hardcoded year value

Marked as reviewed by hirt (Lead).

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PR: https://git.openjdk.java.net/jmc/pull/190