Rearranging test directories

Added test_nm and test_ovro directories. Moved generate_from_dada script

Signed-off-by: Danny Price <dan@thetelegraphic.com>
Fixed YY - YX crossmapping in readdada

YY and YX data were cross-mapped in read dada method of ledafits (thanks Jayce for noticing this).

Signed-off-by: Danny Price <dan@thetelegraphic.com>