Add direct file reading to HSI Cube

[https://me.yahoo.com/postrockrob#52e3a]

Need a way to read HSI cubes without using mmap -- currently the mmap stuff is imbedded into HSI.Cube and not easy to work around without putting a lot of if statements in there (which wouldn't be elegant at all). Need to change the cube loading so that HSI.Cube can determine for itself what data loading it should use; for instance if mmap results in a memory error, it could fall back to direct file reading.

[rob]

(In [1510]) Refs #493: added CubeReader? abstract class * modularized mmap stuff into MMapCubeReader * added stub for FileCubeReader? * removed BIPCube, BILCube, BSQCube and placed their functionality into the MMapB**CubeReader? classes * changed Cube.open to use the Cube.getCubeReader to find a suitable CubeReader?

[rob]

(In [1511]) Refs #493: Added direct file access FileBIPCubeReader * added BIP/BIL/BSQMixins for locationToFlat/flatToLocation

[rob]

(In [1510]) Refs #493: added CubeReader? abstract class

• modularized mmap stuff into MMapCubeReader
• added stub for FileCubeReader?
• removed BIPCube, BILCube, BSQCube and placed their functionality into the MMapB**CubeReader? classes
• changed Cube.open to use the Cube.getCubeReader to find a suitable CubeReader?

[rob]

(In [1511]) Refs #493: Added direct file access FileBIPCubeReader

• added BIP/BIL/BSQMixins for locationToFlat/flatToLocation

[rob]

(In [1512]) Refs #493: added FileBILCubeReader

• updated comments in FileBIPCubeReader
• added default implementation of getLineOfSpectraCopy
• changed Cube.getCubeReader to attempt to open the file so we can trap for out of memory errors
• added Cube.getCubeReaderList as classmethod to list potential cube readers

[rob]

(In [1513]) Refs #493: added FileBSQCubeReader

[rob]

(In [1515]) Refs #493: vfs may return file-like objects, so added getNumpyArrayFromFile to replace call to numpy.fromfile (which can use only actual file handles)

• added check for file offset if using a WindowReader? instead of a real file pointer