Summary
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Define a means for applications to specify property files encoded in UTF-8,
and extend the ResourceBundle API to load them.


Motivation 
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The platform has for a long time provided a properties-file format that is
based on ISO-8859-1 and provides an escape mechanism for characters that
cannot be represented in that encoding. This format is supported by the
standard resource-bundle lookup mechanism. As noted in the related RFEs, this
format is difficult to use because it requires continuous conversion between
its escaped form and text in character encodings that are directly editable.

Description 
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Change the default file encoding for ResourceBundle class to load properties
files from ISO-8859-1 to UTF-8. By doing so, applications no longer need to
convert the properties files using the escape mechanism. Existing properties
files are rarely affected by this change, since ISO-8859-1's U+0000-U+007F are
compatible with UTF-8, and characters whose code points are over U+00FF should
have been escaped.  If an exception occurs on reading a properties file in
UTF-8, either a MalformedInputException or an UnmappableCharacterException,
the properties file is read again from scratch, reverting to using ISO-8859-1
encoding. In order for a rare occasion where a ISO-8859-1 properties file can
be recognized as a valid UTF-8 file, this JEP provides a means to explicitly
designate the encoding either ISO-8859-1 or UTF-8, by setting the system
property "java.util.PropertyResourceBundle.encoding".