and introduce the StringRef struct.
It's more efficient.
Also, rename the `HasName` protocol to `HasShortDescription`, which introduces the new requirement `shortDescription`. This is need because `name` now has `StringRef` type and not `String` anymore
Improve block/instruction lists and similar collections
* pretty print collections in the form “[a, b, c]”
* also do this for lazy sequences
* define a custom Mirror
* in a collection, only print the name of blocks, functions and globals (instead of the full object)
* replace `BasicBlock.reverseInstructions` with `BasicBlock.instructions.reversed()` - in an efficient way
