Change output, add more metadata

Samples have emitXX tasks that emit sanitized versions of the
samples for various build environment (e.g. emitAnt). This change
makes the emit tasks put their output in platform/developers/build/out
rather than in each individual sample's build directory.

Also included: _index.jd creation.

Change-Id: Id1ec3588f682202fc82b7ba868cdaae8e7c579fc
11 files changed