Allow profiling of queries via the API

[oren]

It is currently possible to profile queries via the go Describe() function but it will nice to have it available from the API.

Here is an example of Neo4J profile command. I think we should first expose it to the console and maybe later on to the web interface.

[robertmeta]

Yep, interesting, moved to feature request forum for now: https://discourse.cayley.io/t/allow-profiling-of-queries-via-the-api/229

[dennwc]

With Shapes in place it's becomes even more relevant. Use #670 to show query plan and use contexts that we pass around to enable profiling hooks to get live query stats.