Add Vaisala GLD360-reader.

[sjoro]

Add a draft-version reader for Vaisala GLD360 (Global Lightning Detection) data.

• Tests added
• Tests passed
• Passes git diff origin/master -- "*py" | flake8 --diff
• Fully documented

[sjoro]

Reader done with test data representing one full day, supported file type is flashes_20170620.txt. This is not the official file type from GLD360 network.

[codecov]

Codecov Report

Merging #687 into master will increase coverage by 0.04%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master     #687      +/-   ##
==========================================
+ Coverage   82.65%   82.69%   +0.04%     
==========================================
  Files         161      163       +2     
  Lines       23435    23491      +56     
==========================================
+ Hits        19370    19426      +56     
  Misses       4065     4065

Impacted Files	Coverage Δ
satpy/tests/reader_tests/__init__.py	98% <100%> (+0.04%)	⬆️
satpy/readers/vaisala_gld360.py	90% <90%> (ø)
satpy/tests/reader_tests/test_vaisala_gld360.py	96% <96%> (ø)
satpy/readers/__init__.py	94.87% <0%> (+1.2%)	⬆️

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[coveralls]

Coverage increased (+0.05%) to 82.696% when pulling 793899d on sjoro:gld360-reader into af826ff on pytroll:master.

[mraspaud]

@sjoro What's the status on this ? I the PR feature-complete ? do you plan to add tests ?

[sjoro]

@mraspaud from my side it done for now. was thinking about possible test(s) for checking the sensitivity for the input format, but i'd like to get some brainstorming help with that.

[mraspaud]

Ok, we can talk about it next week.

[sjoro]

Added a test for the file handler.

[sfinkens]

Nice work! One general idea: What about adding time, longitude and latitude as non-dimensional y-coordinates to the power dataset?

xarr = xr.DataArray(da.from_array(self.data['power'],
                                  chunks=CHUNK_SIZE), dims=["y"])
xarr['time'] = ('y', self.data['time'])
xarr['longitude'] = ('y', self.data['longitude'])
xarr['latitude'] = ('y', self.data['latitude'])

You would have to set units and standard name manually though.

[mraspaud]

Looks good, just some nitpicking.

[sfinkens]

Another nitpicker... 😄 Otherwise LGTM!

[mraspaud]

LGTM

[mraspaud]

@sjoro can you add this reader to the reader table in the index.rst file (in the doc) ?