Add and use 0802 nt tiepoints for AMSR2

[trey-stafford]

Add NT tiepoints for use with NSIDC0802 and make that tiepoint set the default when am2 is passed as satellite to nt.tiepoints.get_tiepoints.

Data were provided by @sc0tts:

c     data ARRAY  
c                   N-AS2, S-AS2  / # AMSR2 L1R base data
      data TB19VW /
     $     185.9, 192.4         ! N-AS2, S-AS2

      data TB19VF /
     $     250.9, 256.4     ! N-AS2, S-AS2

      data TB19VM /
     $     222.2, 246.7     ! N-AS2, S-AS2

      data TB19HW /
     $     120.5, 118.2     ! N-AS2, S-AS2

      data TB19HF /
     $     235.5, 240.9     ! N-AS2, S-AS2

      data TB19HM /
     $     200.7, 214.6     ! N-AS2, S-AS2

      data TB37VW /
     $     210.5, 208.7     ! N-AS2, S-AS2

      data TB37VF /
     $     241.3, 246.2     ! N-AS2, S-AS2

      data TB37VM /
     $     188.6, 212.4     ! N-AS2, S-AS2

[trey-stafford]

Issue to address: #70