assertRaw() etc emit '%s found' as default message

Several messages from the assertions in DrupalWebTestCase emit literal percent signs (%):

assertRaw() emits '%s found'
assertNoRaw() ALSO emits '%s found' (ie: should be NOT found, too)
assertPattern() emits 'Pattern %s found'
assertNoPattern() emits 'Pattern %s not found'

Other methods don't create good default messages when none are passed:

assertTitle()
assertFieldBy[No]XPath()
assert[No]Field()