Move SDK system-image source.prop_templates in their own folder.

This allows to have a different rule to generate the source.properties
based on the templates and place them in a directory that depends on
the current target CPU ABI. In turn this prevents the build from
mixing different source.props when building different targets.

(cherry picked from commit 26bcf6a51141fa9dec7df8b932835ccd7b1ab182)

Change-Id: I6e424c16fba17f5d2f37742b7d32208b126bea77
14 files changed