Make focus-related test cases succeed in Firefox

Firefox throws an exception if an element to be focused is not visible or not
in DOM at all. This patch fixes three test cases: two by accepting the
exception as valid, one by making sure the element is visible.

Change by Adrian Lang. Ported from https://gerrit.wikimedia.org/r/#/c/105945/
Adjustment to changes in DataValuesJavaScript

ValueView requries dataTypes apart from this change already. This dependency will be removed
in a future change.
Merge pull request #4 from wmde/datatypesdep

Adjustment to changes in DataValuesJavaScript
Added .jshint file
Added util.Notifier

Added a copy of dataValues.util.Notifier from DataValuesJavaScript to ValueView since it is used
in ValueView exclusively and will be removed from DataValuesJavaScript.
Some clean-up
Merge pull request #5 from wmde/jshintfile

Added .jshint file
Merge pull request #6 from wmde/notifier

Added util.Notifier
Merge pull request #3 from wmde/firefoxtest

Make focus-related test cases succeed in Firefox
Use DataValuesJavaScript 0.2
Merge pull request #7 from wmde/adjusttodatavaluesjs

Use DataValuesJavaScript 0.2
Update README.md
Use value formatters for formatting commons media links

Bug: 49186
Correctly handle null values in _parseValue
Merge pull request #9 from wmde/parseNullValue

Correctly handle null values in _parseValue
Merge pull request #8 from wmde/commonsMediaFormatting

Use value formatters for formatting commons media links
improve the way we get remoteExtPath for resources
Merge pull request #10 from wmde/remoteExtPath

improve the way we get remoteExtPath for resources
Restructured files and directories
Fixed path to util.Notifier test