Change [NSArray arrayWithObject:] to @[] literal

Note: [NSArray arrayWithObjects:...,nil] is left unchanged as that could possibly cause a NPE if converted to @[]
Replace some NSDictionaries with literals

* [NSDictionary dictionary] → @{}
* [NSDictionary dictionaryWithObject:forKey:] can safely be replaced. object==nil would have already thrown a NPE in the past.
* Also replaced some (hopefully safe) NSArray initializers (ie. their objects should always exist).