Color the annotation bolt (#3590)

closes #3590 

Makes it easier to distinguish between annotations while
editing and using them; Uses the icon color.

Merge branch 'ssl-for-mysql' of https://github.com/improbable-io/grafana into improbable-io-ssl-for-mysql

Remove warnings when scanning for plugins in the default
catalog data/plugins

closes #3663

symlinks outside to plugin folder can cause problems.
This commit makes sure to warn about it in the logs

closes #3553

Docs: add example with filter in ES template

(prometheus) fix Prometheus link

Updated copyright to 2016

Fixes #2818.  Adds support for mysql backends via unix sockets

Issue 3461: Session table is now created automatically

Use ssl_mode for mysql and add docs
add docs for the new parameters in config

Tolerate ssl_mode without client authentication

Client cert is not necessary for a SSL connection. So we tolerate
failure if client cert is not provided.
Improve error message if missing server_cert_name and mode is not
skip-verify.

Zoom out on double click in graphs