DERBY-6213: Deprecate support for Java 5 and CDC

Remove reflection code that guards access to the BigDecimal class,
which is now available on all supported platforms.

Remove J2SEDataValueFactory and move all functionality to the base
class DataValueFactoryImpl.

Remove initalization code for DECIMAL in DataValueFactory.boot(), no
longer needed since there is just a single implementation of the
DECIMAL type.

Make the parser represent DECIMAL literals as BigDecimals instead of
Strings.

Remove now unused methods in DataValueFactory for constructing
SQLDecimal values from String values.

Clean up references to CDC in comments.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1516715 13f79535-47bb-0310-9956-ffa450edef68