Removed TinyMCE dependency of body field, using plain textarea instead

Using BlankProfile with current PW dev version (2.4.9) throws an error/hint, because it is expecting 'InputfieldTinyMCE'. This commit sets the body's input field class to a generic 'InputfieldTextarea'. Maybe to replace with 'InputfieldCKEditor' once ProcessWire 2.5 is officially released. But in order to leave this site profile really *blank*, a body field with just a generic textarea would fit, IMHO.