RFR (JDK10) 8183743: Umbrella: add overloads that take a Charset parameter

Hi, Adding convenient methods that take a Charset to several classes that have already had methods with a Charset/Encoding name as a parameter. To avoid any impact on compatibility and JCK tests, we've kept the existing methods virtually untouched except making a reference to the new ones to encourage the use of these new methods going forward. The javadocs of the new methods however, may be more complete with details on handling edge cases / Exceptions. JBS: https://bugs.openjdk.java.net/browse/JDK-8183743 webrev: http://cr.openjdk.java.net/~joehw/jdk10/8183743/webrev/index.html Thanks, Joe