Added ability to enable/disable segment generation at runtime

[tomkoufakis]

Changes:

• Added support for passing in an options object containing an enabled field. This will allow enabling/disabling metrics gathering programatically. This is implemented as an options object in order to allow future expansion of other configurations.
• Added ability to view the html coverage report via npn run coverage_report --> coverage/lcov-report/index.html

Usage:

In your schema.js/ts:

`
import traceResolvers from '../../src/traceResolvers';

// module scope or other storage mechanism of your choosing
export const tracingOptions = { enabled: true };
...

traceResolvers(schema, tracingOptions);
`