Update API endpoint for creating DVSections and DVCharts

[AleksueiR]

Right now, DQV exposes corresponding classes on the API which require the use of the new keyword:

const dvchart = new DQV.Chart({ ... });
const dvsection = new DQV.Section({ ... });

@alyec has pointed out that in many cases the reference to a DVChart object is not needed on the host page (DQV keeps track of them internally), so the calls end up like this:

new DQV.Chart({ ... });
const dvsection = new DQV.Section({ ... });
dvsection.mount( ... );

This invokes the wrath of the tslint's no-unused-expression rule.

Update DQV endpoints to expose a function instead of the class, which also returns the newly constructed object. Being a simple function call, it obeys the rule and doesn't look as offensive as a snowman.

DQV.Chart({ ... });