RFR: 8170251: Add javax.tools.Tool.name()

[Jonathan Gibbons]

Please review this small fix to add a new default method to javax.tools.Tool
to get the name of the tool, and implement that method for the javac and
javadoc tools. Also, declare javac and javadoc to "provide" 
javax.tools.Tool.

JBS: https://bugs.openjdk.java.net/browse/JDK-8170251
Webrev: http://cr.openjdk.java.net/~jjg/8170251/webrev.00/

-- Jon