luci_deploy: Enable loading "index.yaml" directly.

luci_deploy: Enable loading "index.yaml" directly.

"index.yaml" is a somewhat special configuration file, in that
`dev_appserver` is able to directly generate it in response to index
operation observations. Rather than force the user to manually translate
between "index.yaml" and the AppEngineResource's Index protobuf, add the
ability to load an "index.yaml" file directly into "luci_deploy".

This will also lower the barrier to migrating existing applciations over
to "luci_deploy".

Along the way, do a little cleanup, and split the AppEngine-centric
code off from deployment-centric code.

BUG=chromium:639981
TEST=None

Committed: https://github.com/luci/luci-go/commit/557281dad2980196744d19babd69da1345b912fa

[dnj, 2016-12-17 08:54:01]

Description was changed from

==========
luci_deploy: Enable loading "index.yaml" directly.

"index.yaml" is a somewhat special configuration file, in that
`dev_appserver` is able to directly generate it in response to index
operation observations. Rather than force the user to manually translate
between "index.yaml" and the AppEngineResource's Index protobuf, add the
ability to load an "index.yaml" file directly into "luci_deploy".

This will also lower the barrier to migrating existing applciations over
to "luci_deploy".

Along the way, do a little cleanup, and split the AppEngine-centric
code off from deployment-centric code.

BUG=chromium:639981
TEST=None
==========

to

==========
luci_deploy: Enable loading "index.yaml" directly.

"index.yaml" is a somewhat special configuration file, in that
`dev_appserver` is able to directly generate it in response to index
operation observations. Rather than force the user to manually translate
between "index.yaml" and the AppEngineResource's Index protobuf, add the
ability to load an "index.yaml" file directly into "luci_deploy".

This will also lower the barrier to migrating existing applciations over
to "luci_deploy".

Along the way, do a little cleanup, and split the AppEngine-centric
code off from deployment-centric code.

BUG=chromium:639981
TEST=None

Committed:
https://github.com/luci/luci-go/commit/557281dad2980196744d19babd69da1345b912fa
==========

[dnj, 2016-12-17 08:54:02]

Committed patchset #1 (id:1) manually as
557281dad2980196744d19babd69da1345b912fa (presubmit successful).