Functional: Wrapping dynarrays, support for collections

Dynarrays: only TArray<> seems to work on XE3, possible compiler
limitation

Collections support: Wrappers will look for enumerables supporting Count
property, and wrap this.
Functional: Added Slice, Enumerable.Select

Slice works similar to Python's islice() from itertools.
Functional: Minor improvement in ordered enumerable

Use Enumerable<T>.ToArray(), which is optimized for collections.