Moving handling of non-integer element size in IE10 to correct place

This change partially reverts revision 26bee3e99aa6, and moves the
rounding of the size to integer values to
webdriver.atoms.inject.dom.getSize.
Adding padding for IE < 8 for getting invisible element location

Element location returns a position 2 pixels off for invisible elements on
IE 6 and 7.
Updating .NET tests to remove RenderedWebElementTest

This makes the .NET tests more aligned with the Java test suite.
Updating IE prebuilts
Ignoring invalid test for IE6.

IE6 doesn't handle fixed-position elements correctly.