bzChecker listener now does not fail when required properties not set

it just prints out exception onTestStart, in other cases it's silent. So
your tests won't all fail because you have this listener enabled, but not
configured it via properties
SkipIf listener: fixed evaulation of equals,notEquals and contains
Merge pull request #3 from lzoubek/master

BzCheckerListener made a little bit more robust + small SkipIfListener fix