Abstracted jopusfile to prepare for in-memory files
Added managed code for buffered files
Midway progress for tonight. Will rebase to remove this commit later.
Implemented memory stream decoder.

Added convenience methods to support to load buffers/decodables from jar, file or existing buffer.

Abstracted native read/close operations to JOpusDecodable, since it seems like memory, http, and file can all use the same common interface.