Add a convenience method for creating arrays with a block

New method essentially obsoletes `-[NSArray arrayByPerformingSelector:(SEL)aSelector withObject:(id)object]` since it is more versatile (allows a whole block of code to be run on each object as opposed to just one method)
add a convenience method for splitting strings on (all) newlines

More effective than -[NSString componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]]
Since it allows for other newline types
Allow strings to have children (lines)
Honour the `objectHasChildren` method before trying to load an object's children

Previously, even if `objectHasChildren` returned NO, → into an object would still load its children (that method was only used to display the > arrow or not). Now, this method is honoured - unless ⌥ is held whilst →.
retain meta objects when accessing
Stop string object IDs being parsed as strings
Check for QSBundleChildPresets when specifying if objects (apps) have children
Merge pull request #1505 from pjrobertson/stringChildren

Children for strings