Issue 85 - Converting user location action links to buttons to fix voice over issues

Changes are:
* Prefer and remove anchors have been changed to buttons, this should fix issues #85, #87 and #90 
* Added an aria-disabled attribute for prefer location button
* Base style for dialog is position: relative (moved from min568) as buttons were displaying above icons.

~~This change introduces an issue which would need to be fixed before this can be merged~~:
* ~~The buttons can be tabbed to (shift tab from the confirm button) when they are behind the dialog, there are a number of options to fix which would need to be done before the dialog is displayed and then reset after~~:
  * ~~Add aria-hidden="true" labels~~
  * ~~Set tabindex to -1 to remove from tab order~~
  * ~~Hide with display: none~~
  * ~~Remove the elements from the DOM~~

~~Not entirely sure which solution is best, any ideas / input?~~

Edit: Fixed with display: none in stylesheet.

Also noticed a couple of other issues (will raise these):
* The buttons could be styled with a larger hit area which would help with touch screens, currently they are the size of the icons.
* When the dialog has been confirmed or cancelled the focus position is lost and then user is put back to the top of the page.