Graph: fix for bars not displaying, caused by change in recent commit, added unit test so it does not happen again

Speed search result parsing

Graph: fixed value formating for tooltip, need original data. flotcharts copys the data, so changes to value formats func after plot call does not affect the plot.getData() series

second parameter of groupByNode() should be 0 indexed

Fix #901: correct positioning for multiple highlighted stacked and staircase points

Reuse ElasticSearch hits length via hits.total and cache it rahter than calculation length every iteration.

New backend call to each keydown may hit the back-end performance.
500ms is reasonable delay to avoid too many requests while user is
typing a search query

Inline styles slow down rendering proportionally to containers number

Css fix for metrics tab, help boxes did extend page height so could not scroll if they extended below screen, #891

Fixed issue casued by recent angular upgrade and stateful filter, casued template vars in graph titles no update properly, angular was not updated in 1.8.1 so this does affect any released version, Closes #892

Conflicts:
	CHANGELOG.md

Dashboard: fix for dashboard schema upgrade during load, ensure that annotation and templating object as a list array, Closes #890

Add a Gitter chat badge to README.md

Dashboard: show error when importing dashboard json file with broken/incorrect json syntax, Closes #878