Update bower.json to depend on jquery not jQuery

It appears Bower will happily resolve *both* jQuery and jquery:
in projects that specify both At.js and other dependencies relying on
jQuery, Bower will attempt to install jQuery twice, possibly with
differing versions.

In the case of a case insensitive filesystem (Windows and Mac, by
default), the jQuery components directory will be overwritten/merged.
See: https://github.com/bower/bower/issues/1150

https://www.openproject.org/work_packages/7310