RFR: JDK-8264838: IGV: enhance graph export functionality

[Nils Eliasson]

Hi,

This patch adds SVG and searchable PDF export functionality to IGV. 

It's originally contributed by rcastanedalo at openjdk.java.net.
I have updated the patch with new library versions, rebased and tested it.

Please review,
Nils Eliasson

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Commit messages:
 - Update versions
 - Merge master
 - Remove unused import
 - Check whether writer is null before closing
 - Update copyright years
 - Add option to export graphs as searchable PDF files
 - Enable SVG exports by default

Changes: https://git.openjdk.java.net/jdk/pull/6564/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6564&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264838
  Stats: 362 lines in 11 files changed: 83 ins; 262 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6564.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6564/head:pull/6564

PR: https://git.openjdk.java.net/jdk/pull/6564