RFR: JMC-5768: Add frequency (Hz) support in UnitLookup

[Elliott Baron]

Hi,

This patch adds support for the Hertz (Hz) unit to represent frequencies 
in JMC. In particular, this new unit is used to support the JavaFX pulse 
phase event (available in OpenJFX 12). The target framerate used by the 
associated JMC rule is expressed in frames per second, and this patch 
changes that to Hz.

There didn't appear to be existing tests for the JavaFX plugin, so I 
created a new test plugin containing a test for the pulse duration rule. 
This test uses a new JFR recording that contains several 
javafx.PulsePhase events with enough long phases to trigger a warning. 
The test verifies that the score and warnings from the rule match the 
expected values.

I have done my best to add/modify localization associated with the new 
unit by researching the appropriate terms in each language online.

Webrev: http://cr.openjdk.java.net/~jmatsuoka/JMC-5768/webrev.02/

How does the patch look?

Thanks,
Elliott