RFR: 8264838: IGV: enhance graph export functionality

[Nils Eliasson]

This PR that is contributed by @robcasloz adds SVG export functionality to IGV.

Please review,
Best regards,
Nils Eliasson

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Commit messages:
 - Remove unused import
 - Update copyright years
 - Enable SVG exports by default

Changes: https://git.openjdk.java.net/jdk/pull/4394/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4394&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264838
  Stats: 302 lines in 11 files changed: 29 ins; 256 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4394.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4394/head:pull/4394

PR: https://git.openjdk.java.net/jdk/pull/4394