add aair:activityContext the 4th and optinal part of an aair:Activity to lib

add more objects and verbs

add classes of new objects and verbs

change feed child nodes

add default cases when reading a feed with unknown objects or verbs

import more attributes of incoming feeds
change static invocation of DOMDocument::loadXML

improve feed factory

fix newFromUrl method,
change static call DOMDocument::load,
add links to to factory