cpp: Add OMEXMLMetadataRoot
xsd-fu: Use absolute namespaces and const getters for C++ metadata
xsd-fu: Add get*Type methods to Shape and LightSource
xsd-fu: Correct C++ property types
xsd-fu: C++ supports const and non-const property retrieval
xsd-fu: Add object header introspection
xsd-fu: Rename property types

langType is langBaseType
langBaseType is modelBaseType
xsd-fu: Add object type namespace properties
xsd-fu: Do not generate trigraphs for templated absolute types
xsd-fu: Correct C++ metadata store types
xsd-fu: Split metadataStoreType into separate argument and return types
xsd-fu: Add assignable type to property
travis: Remove python version requirement

Travis recently changed how python is supported, but apparently
what we were doing never actually worked: if you specify java
as the language, the python block is ignored.  So we're stuck
with whatever the build environment for the specific java
version provides.  This patch removes python from the matrix
excludes, which should restore the matrix exclusions.
merge develop -D org -I include -E exclude: PR 528 (Tile performance improvements for VMS and NDPI)
merge develop -D org -I include -E exclude: PR 834 (Permit cppwrap failure)
merge develop -D org -I include -E exclude: PR 847 (Fix the copyright statement on generated Javadocs (rebased onto develop))
merge develop -D org -I include -E exclude: PR 848 (xsd-fu: Further work for C++ metadata store generation)
merge develop -D org -I include -E exclude: PR 849 (travis: Remove python version requirement)