Expose fine-tuning knobs in Cocaine extensions.

Allow Cocaine extensions users to configure various Elliptics client
settings, such as timeouts and thread counts.
Merge pull request #160 from Kobolog/master

Expose fine-tuning knobs in Cocaine extensions.
Explicitly stop engine upon dnet_app_t destruction
Merge branch 'master' of github.com:reverbrain/elliptics
v2.24.10.4
Merge branch 'master' of github.com:reverbrain/elliptics