Add new "changed" function

This function checks if a metric has changed and returns 1 when it changed else 0
Merge pull request #838 from gwaldo/0.9.x

0.9.x - Merging in docs on Synthesize and Windows Hope
Number of results from cache query was incorrectly logged
Merge pull request #840 from Kixeye/0.9.x-carbon-cachequerylogmsg

Number of results from cache query was incorrectly logged (0.9.x)
Improved documentation for cactiStyle

Explained possible options for system (not letting the reader hunt around for
possible values), as well as culled most info for alignment from:
https://github.com/graphite-project/graphite-web/issues/671
Improved documentation for areaBetween
Merge pull request #842 from ojilles/0.9.x

0.9.x backport of documentation updates
Minor fix for Vagrant+Syntesize docs
Allow metric finder to return jsonp objects

Needed for cross-domain ajax calls

Fix jsonp response format
Documenting that you can use alpha values for colors in colorList and bgcolor.
Merge pull request #845 from deniszh/0.9.x_doc_fix

Minor fix for Vagrant+Syntesize docs, backport pull request 844 to 0.9.x.
Merge pull request #847 from ojilles/0.9.x

Documenting that you can use alpha values for colors in colorList and bg...
Rework of 'query-bulk' implementation for 0.9.x

Please see issue #378, I just reworked for latest 0.9.x branch and made configurable. Corresponding change for carbon was merged by @mleinart while ago - https://github.com/graphite-project/carbon/pull/132
Replacing #824.
Backport of pr #495 to 0.9.x branch

Fixes issue #220
Merge pull request #851 from deniszh/0.9.x_HWA_fix

Backport of pr #495 to 0.9.x branch
Merge pull request #846 from kali-hernandez-sociomantic/jsonp

Allow metric finder to return jsonp objects
Merge pull request #850 from deniszh/0.9.x_query_bulk

Rework of 'query-bulk' implementation for 0.9.x
Merge pull request #530 from criteo/changed-function

Add new "changed" function
remove superfluous grid line for log scale, refs #389
Merge pull request #867 from obfuscurity/backport_log_scale_labels_fix

Remove superfluous grid line for log scale