[Vxl-maintainers] vil_nitf2 test cases

[Rob R. <ro...@st...>]

I added code to vil_file_format so it now recognizes the new vil_nitf2_image
class.  I also added a number of test cases for NITF 2.x reading.  The test
cases cover the following items:

- All four uncompressed data layouts
  - Band sequential (IMODE=S)
  - Band interleaved by block (IMODE=B)
  - Band interleaved by pixel (IMODE=P)
  - Band interleaved by row (IMODE=R)
- A good sampling of data types
  - 8 bit unsigned int
  - 16 bit unsigned int
  - 32 bit signed int
  - float
  - double
- One case where the "actual bits per pixel" is less than the "number of
bits per pixel" and data is right justified
- Both NITF 2.1 and 2.0 files

I created all the test files myself so that they would be very small (less
than 1kb each).  There are a few more tests I'd like to implement, but this
is a good start.

Rob