Update unrecognized arguments error from argument file

Surround fromFilePrefixChars with square brackets because they
can be multiple characters.
Add public static ArgumentParsers.DEFAULT_PREFIX_CHARS

It is the default value of prefixChars which can be passed to
ArgumentParsers.newArgumentParser().
Format error message according to column width
Disable terminal width detection in ArgumentParserImplTest
Document ArgumentParsers.DEFAULT_PREFIX_CHARS in usage