Fix incorrect raw read on RegionFile

By not setting the limit in the compressed buffer, the raw read
would read past the compressed data.

Additionally, make the type header allocation lazy to avoid
allocating disk space to headers that are not in-use.

Fix failure to write internal data at 1024 sectors

The buffer limit is incorrectly set, it should be set to +1
of the max size before external allocation must take place.

Add copy option for conversion to SectorFile

The copy option does not perform decompression/recompression,
which should make it faster for systems limited by CPU resources.

Additionally, read the entire RegionFile into memory when converting
to SectorFile to avoid random read costs when converting.

Rename file extension to sf and sfe