Updated UVW computation and numerous other mods

leda/interfits.py:
* Added initialize_site() method -- this creates a pyEphem observer. For LEDA, it will load the data from JSON config files. Otherwise, it will use ecef2geo (Bowring's method) to compute lat-long-elev

lib/coords.py:
* moved generateBaselineIds() to coords
* updated computeUVW() -- now faster (no longer does matrix calc). Removed old version. Will now accept numpy arrays of baselines xyz vectors
* added computeBaselineVectors() method
* very basic unit-test for computeBaselineVectors() in test/00_test_coords.py

qtuv.py
* Now uses ledafits as default, so can read dada files without panicking.

test_nm/
* miscellaneous test stuff. test_phs2src.py is of particular note, it tests the phasing routines (UVW coordinates),
* Test of dada writer vs. old lconverter method - compare_lalc_dada.py. Seems to suggest dada reader is ok...

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