Add JUnit test support

[magreenblatt]

Original report by me.

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To ensure the quality of JCEF we should begin writing unit tests. JUnit seems a reasonable choice as it appears to support the functionality that we need and can be integrated with a number of different IDEs and build systems.

[magreenblatt]

Add initial JUnit test support (see issue #339).

Unit tests can be run from the command line using the run_tests.[bat|sh] script. Currently supported on Windows and Linux only.

Known issues:

• Linux: TestFrame hangs due to the onBeforeClose event not being delivered.

→ <<cset d0f5129e0d06 (bb)>>

[magreenblatt]

• edited description