Prometheus: Rework interval and step computation

Add milliseconds format in table panel's config

Update script to make it use OpsGenie's REST API

This changes introduce milliseconds format option in table panel
config GUI. Current grafana support milliseconds in time and
actually used at graph panel, however current table does not
provide the way to show milliseconds. This fix is to add format
in table panel to show milliseconds in table as well as graph.

adding support for token-based slack file.upload API call for posting images to slack

* colorpicker: initial picker with predefined palette and spectrum

* colorpicker: highlight selected color

* colorpicker: add onChange() callback

* colorpicker: replace singlestat picker by new one

* colorpicker: style tweak

* colorpicker: parse color on input blur

* colorpicker: sort palette by hue and lightness

* colorpicker: refactor, move colors sorting to 'app/core/utils/colors'

* tech: colorpicker - fix linter errors

* colorpicker: convert to React components

* colorpicker: fix spectrum import after moving to webpack

* colorpicker: minor refactor

* colorpicker: initial series color picker

* colorpicker: fix tests error

* styling changes and some text changes

* styling changes

* fixing checkboxes

* deleted old file, fixed checkboxes

* minor change

The script is making API calls to the deprecated OpsGenie Web API, we updated the script to make it use new OpsGenie's REST API.