Revision 1854668

Improved: Disallow extension of the script helper bindings (OFBIZ-10825)

‘ScriptHelper’ is a mechanism used to add some useful bindings to
scripts.  This feature has been introduced in revision 1299924 by
Adrian Crum as part of an general effort of supporting the Generic
Scripting Engine specified by JSR-223.

Previously this mechanism was extensible, however it appears to be
undesirable (nor used in practice) to extend the bindings available to
services since the internal service implementations are highly coupled
to those bindings.  As a consequence the usage of the Abstract Factory
pattern which was used for that purpose is now removed.

The side effect of this change is that we have now simpler code.