Bug 1016184 part 3f - Fix test_paste_selection.html

To avoid the appearance of the touch caret interfering with the
synthesized mouse event position, add spaces between <input> fields, and
make the event at the center of the pasteArea.
Bug 1016184 part 3g - Enlarge expiration time in mochitest and reftest
Bug 1016184 part 4 - Enable touch caret by default on b2g