RFR: JDK-8285932 Implementation of JEP-430 String Templates (Preview)

[Jim Laskey]

Enhance the Java programming language with string templates, which are similar to string literals but contain embedded expressions. A string template is interpreted at run time by replacing each expression with the result of evaluating that expression, possibly after further validation and transformation. This is a [preview language feature and API](http://openjdk.java.net/jeps/12).

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Commit messages:
 - Tabs to spaces
 - Force processor before template string expression
 - Correct implNote
 - Add valueGetters method
 - Added RAW template processor
 - Merge branch 'master' into 8285932
 - Rename to ValidatingProcessor
 - Javadoc mistakes
 - Rename TemplateProcessor
 - Clean up tests
 - ... and 4 more: https://git.openjdk.org/jdk/compare/0c13d666...7b2011ac

Changes: https://git.openjdk.org/jdk/pull/10889/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10889&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8285932
  Stats: 7452 lines in 74 files changed: 7263 ins; 45 del; 144 mod
  Patch: https://git.openjdk.org/jdk/pull/10889.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10889/head:pull/10889

PR: https://git.openjdk.org/jdk/pull/10889