Modify constructors for Unique/Proportional
Modify constructors for classifications

Note that with these new constructors, for Interval Classifications, the
interface is constructed correctly, but I have a ParseException in the
CanvasSE class (even though I haven't touched CanvasSE). Beginning of
the stacktrace:

    ERROR gui.class org.orbisgis.view.toc.actions.cui.components.CanvasSE  -
    org.gdms.sql.engine.ParseException: Parse error on line 1 at character 42:
        found ',', expected ';'.
	at org.gdms.sql.engine.step.parsing.ParsingStep$.doOperation(
        ParsingStep.scala:64)