RFR: JDK-8055298 - develop inital set of UART tests

[Stas Smirnov]

issue: JDK-8055298 <https://bugs.openjdk.java.net/browse/JDK-8055298>
webrev: 8055298 <http://cr.openjdk.java.net/%7Estsmirno/8055298/>

Hi All,

Need a review for an update.
In this update I have implemented all currently required testcases for 
UART testing.

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Best regards,
Stas Smirnov

Stas Smirnov | Java Embedded
Phone: +7 812 3346130 | Mobile: +7 921 9262241
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