If an element isContentEditable, do not ignoreScrollStart incase users
are using contenteditable elements to scroll. This may have originally
been put in because it disabled text selection, and moving the text
cursor on touch. But this doesn’t seem to be the case anymore, so it
may have been put in for platform versions we no longer support. Also
fix the data-prevent-scroll dataset attribute. Closes#2091
Many services/directives have to interact with the body element, and
each one has to write the same long code. The $ionicBody service
provides some useful methods to clean up and reduce redundant code.
