implementation of default locators + Table.row_count

[tempredirect]

I've been working on improving the safariwatir spec compliance.

• implemented the default locators for all the current element types browser.div('an_id') browser.form('form_name') etc The code is almost a straight port from watir.
• implemented 'locate' purely for spec compliance, doesn't actually mean quite the same thing in safariwatir
• implemented Table.row_count