Ability to set a low limit for Elasticsearch date histogram interval

fix(solo panel): fixed solo panel view gray bottom for rendered image and embedd iframe scenarios, fixes #3004

fix appending query strings in linkSrv

Fixed docs typos

closes #2901

fix(elasticsearch): fix for daily pattern when getting index for today, is now using utc, fixes #2913

influxdb: fix influxdb annotation query

When linkSrv appends parameters to a URL's query string, it would blindly
add a ? to the URL even if the URL already contained a ? or the string
to add was empty. This change fixes that behavior and some other edge cases.

Includes a unit test to verify expected behavior.

docs(): Fix changelog link in whats-new-in-v2-1

I noticed a typo when I was reviewing the docs ...

fix(build): minor fix for build script to make latest copy for rpm when version is pre release version

fix(panel): fix for firefox and placing cursor in text inputs when in panel fullscreen edit mode, fixes #2957

Add tests to exercise new units as well.

Abstract out both decimal and binary SI prefixes into builders using
scaledUnits.