Generate binding-dom-codec classes into separate packages

Generate binding-dom-codec classes into separate packages

We are namespace-squatting on the codegen namespace, adding various
magic suffixes to ensure uniqueness. This is not perfect, because
compile-time codegen does not have a completely free reign over
its namespace. This is also problematic if these classes were delivered
through a separate jar -- it would cause split packages, which are
ugly.

Allocate three new namespaces and dump codec classes there, thus
ensuring no overlap, squatting or similar.

JIRA: MDSAL-784
Change-Id: I68b8db09ffc9286bb40118545619760b9060a082
Signed-off-by: Ruslan Kashapov <ruslan.kashapov@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>