Handle UUID in string Node

If String is an UUID, try to find the Node by identifier.
CS fix
Removing obsolete 'if' statement

I think that would suffice... But in that case all of multiple valued strings would have to be uuids of existing nodes... If we want to get nodes from ie. array(<uuid>,<path>), we should loop through $values, as David said...
enable testing on hhvm and cleanup some tests to not rely on weird zend php behaviour
Merge pull request #204 from jackalope/hhvm

test on hhvm
commens added, obsolete use removed
Handle mixed collections of UUIDs and Paths

Think, this will suffice...
Merge pull request #205 from eXsio/patch-1

Handle UUID in string Node
Better descriptors