lint errors, fixed error with plot domain, simplified interfaces...
lint errors, fixed error with plot domain, simplified interfaces...

JSLint errors were mostly useless, but revealed a few minor problems.

Plot domain with no graps selected would contain NaN and cause console
to spew errors, which was fixed bt providing a default domain [0, 1].

Simplified interfaces: now dataSource and renderLoop `start()` methods
accept functions instead of objects or using a global value.
This weakens a link between components.

Fixed a potential error with dataSource being stuck because
requestInProgress flag not being cleared during `stop()`.

devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware