RFR: Data plugin

[Alexandre Iline]

* JREInstr
 * instrumentation plugin enhancement
 * build script
 * Implantable interface
 * support for all data types
 * other minor enhancements

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Commit messages:
 - requireNonNull
 - cleanup
 - Merge branch 'master' into data-plugin
 - in- and out- files
 - support for loading environment from an implanted property file
 - More implantable classes.
 - workaround for CODETOOLS-7903035
 - JREInstr
 - Removed empty test method
 - Removed unused imports, old version of a test.
 - ... and 1 more: https://git.openjdk.java.net/jcov/compare/f3ee5df6...4b45ff92

Changes: https://git.openjdk.java.net/jcov/pull/19/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcov&pr=19&range=00
  Stats: 1461 lines in 41 files changed: 1141 ins; 167 del; 153 mod
  Patch: https://git.openjdk.java.net/jcov/pull/19.diff
  Fetch: git fetch https://git.openjdk.java.net/jcov pull/19/head:pull/19

PR: https://git.openjdk.java.net/jcov/pull/19