Add decorating "type" attr extension for service refs

Add decorating "type" attr extension for service refs

Added an attribute extension to the <service> element that adds an
OSGi service property of the form "type=<value>". This allows providers
of a service to advertise the type of the service to distinguish it from
other services provided for the same interface.

Conversely, the extension can also be used in <reference> elements to allow
consumers of the service to specify which service implementation they
want.

As a convention, the "default" type should be used for the default
implementation of the service with other types being specialized
implementations. This allows consumers to obtain whichever
implementation the provider deems as the default without having to
explicitly know it and allows the provider to switch to a new
implementation without requiring all consumers to change their
referenced type.

If a consumer doesn't specify the "type" attribute, it may be ambiguous
as to which service is obtained. Rather than requiring that the "type"
attribute be specfied for every <reference> element, I added an attribute
extension attribute, "use-default-for-reference-types", to the <blueprint>
element that automatically adds a filter to all <reference> elements where
the "type" property is either not set or set to "default" if the "type"
attribute isn't explicitly specified. This ensures the default implementation
is imported if there are other implementations advertised with other types.

Change-Id: Ie61bb45da1c7539732cd31ab0f8130233c9696fc
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>