doc: First pass at updating Java documentation. * doc/interpreter/java.txi: Remove deprecated functions from documentation. Add FIXME notes. Replace @var with @file macros. Trim long lines. Use Octave documentation conventions throughout. * scripts/deprecated/java_get.m, scripts/deprecated/java_new.m, scripts/deprecated/java_set.m: Change seealso references to only refer to supported, non-deprecated, functions.