xsd-fu: Set current language and add class properties property

The current language global permits the model classes to know which
language they should be using without having access to the
command-line options object.

The class properties (instanceVariables) details the language-
specific instance type, name, default value and comment for
each class member.  This removes the need for the code to
determine these values to be duplicated in the template for
each language and for each time they are needed which greatly
simplifies the template.
xsd-fu: Improve C++ source generation

The main Pojo template was processed twice for header and
source generation.  This patch does the same for class-
specific custom content.
xsd-fu: Add C++-specific enum_includeall target

This target generates "enums.h" which includes all generated enum
headers.  This is needed for C++ since unlike java it's not
possible to include all headers within a namespace.  This patch
does not include the template itself.
xsd-fu: The default package is ome.xml.model

This is being set by hand when run xsd-fu via ant; this change
simply makes it the default internally as well.
xsd-fu: Remove java comment in description
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 572 (2013-06 schema links)
merge develop -D org -I include -E exclude: PR 573 (bfopen: save individual series' original metadata)
merge develop -D org -I include -E exclude: PR 574 (xsd-fu: Generalise language type mapping)
merge develop -D org -I include -E exclude: PR 577 (Update auto-generated documentation)
merge develop -D org -I include -E exclude: PR 578 (xsd-fu: Generalise language type mapping (2))