Preview release 0.1.11

Partition physical-file -> logical-files in load()

The dlis standard have a concept of logical files. A logical file is a
group of related logical records, i.e. curves and metadata and is
independent from any other logical file. Each physical file (.dlis) can
contain 1 to n logical files.

load() now returns a tuple-like with one file-handle pr logical file
in the physical file.