Allow NIOFileHandle's buffer size to be passed through from RAIS

This lets us set a buffer size for a specific stream/handle, instead of
calling the static setDefaultBufferSize method in NIOFileHandle.
CZI: use a buffer size of 1024 in most places

We have to do a lot of seeking and opening new streams to read a small
number of bytes; the only place where large chunks of bytes are read is
when the pixel data is processed.  This should speed up setId times, as
we're not attempting to buffer 1MB every time a new stream is opened
(potentially millions of times for very large datasets).
Improve master file detection
Revert to accepting unknown compression types as raw data

...instead of throwing an exception.  Many of the camera-dependent
encoding types are just raw data, and were correctly handled previously.