cpimport now has the ability to use libmarias3 to read an object from an
S3 bucket instead of a file on local disk.
This also moves libmarias3 to utils/libmarias3.
It turns out -c wasn't actually connected to anything and now with have
BLOB/TEXT it is pretty useful. If -c is set to < 1MB then 1MB is used,
otherwise it will use the selected buffer size.