Added support for UTC date time labels.

  * dygraph-utils.js:
    new utc switch parameter for `Dygraph.dateString_`
    and new signature for `Dygraph.hhmmss_`.

  * dygraph.js:
    support for UTC date time labels in date formatter.
    Also rename it to `dateAxisLabelFormatter`  for homogeneity
    with the numeric one. and add  a `dateValueFormatter`.

  * dygraph-options-reference.js:
    new `labelsDateUTC` option.
Added support for option `labelsDateUTC` to the date tick picker.

    * dygraph-tickers.js:
      simplified date tick generation. `Dygraph.getDateAxis`
      now produces nice ticks both in UTC and local time.

    * dygraph-utils.js:
      removed `Dygraph.dateSetters` and `Dygraph.setDateSameTZ`
      because they are not needed any more.
x axis log scale.
Merge branch 'master' into xlog

Conflicts:
	dygraph-layout.js
dingle quotes.
Legend follows highlighted points
Missing semicolon
Merge branch 'crosshair'
gitignore
added synchronize-Charts.html and customLabel_Crosshair.html from  http://www.pixeltradr.com/dygraphs/tests/
Revert "added synchronize-Charts.html and customLabel_Crosshair.html from  http://www.pixeltradr.com/dygraphs/tests/"

This reverts commit 6a90350a56528606eab58a5eb9413f326f06df2f.
Revert "gitignore"

This reverts commit 9b40c7367f8e2b97789de063e72d96ef4d9ba1ba.
Arrow shape
don't create annotation div if there are no 'icon' or 'shortText' property
Canvas Annotations Plugin
Tests for Canvas Annotation Plugin
Fixed #4
Mind renaming.
Canvas annotations and synchronize demo
Set annotations on multiple series at once