fix #859 test.aria.utils.Dom failure in some browsers

Method `getStyle` was giving the wrong values for `"backgroundPositionX"` and `"backgroundPositionY"`.
On top of that, even on modern borwsers, a null value is returned in some cases even when a value is available.
fix test.aria.html.textinput.placeholder.PlaceholderTestCase randomly failed in IE9
fix #861 test.aria.templates.validation.errortext.ErrorTextTestCase failure in Chrome

The test was failing because the synthetic type (with the robot) was not working. Clicking on the field first makes it work.
doc `preloadSkinImages` writes to `<BODY>`

Close #854.
fix #863 test.aria.popups.Popup failure in IE7

The bean for popup configuration has also been updated.
v1.4.13
fix #866 Changing message when user tries to load a library already loaded

Changing from an error to a warning message since it's not breaking anything and the framework continues working properly.
fix #770 Multiple embed:Elements linked to page engine instances cause widget errors
fix #812 IE11 failing test.aria.widgets.form.textinput.onchange.OnChangeTestCase
fix #815 IE11 failing test.aria.widgets.form autocomplete.selectionKey.AutoComplete
fix #816 IE11 failing test.aria.widgets.form autocomplete.selectionKey.AutoCompleteModifier
fix #817 IE11 failing test.aria.widgets.form.autocomplete.spellcheck.SpellCheckTestCase
fix #818 IE11 failing test.aria.widgets.form.autocomplete.expandbutton.test2.ExpandButtonCheck
fix #819 IE11 failing test.aria.widgets.form.autocomplete.handler.test1.LCHandlerTestCase
fix #820 IE11 failing test.aria.widgets.form.autocomplete.caret.CaretTestCase
fix #886 jsdoc problem inside Browser class

Fixing the class description for aria.core.Browser

close #887