Fix undefined variable errors when using --cookies and --scroll
Add --execute to execute some javascript when the page is loaded.

This allows filling fields, scrolling in a div, etc.
Put the directory of the cursors in a variable.

Also move the cursors into a cursors/ directory, and put the original
copyright notice from Jimmac.
Make it possible to use an element id with --point

This makes it much easier to simulate pointing a random element.
Display a hand pointer in the capture when style says so.

According to the computed style of the element the pointer is hovering,
we choose the pointer to display. Currently only the pointing hand and
the left arrow are supported.