added coordinates module, with tests

[aqreed]

added the following functions for coordinates transformation:

• lla2ecef
• ned2ecef
• body2ned
• ned2body
• body2wind
• wind2body

[aqreed]

I have added the following function (with its tests):

• ecef2ned

Also, improved tests for ned2body, body2ned, wind2body, body2wind and ned2ecef functions

[aqreed]

Added the az_elev_dist function (with tests)

[aqreed]

@jorgepiloto, I have updated this PR after #39. Builds are passing except TOXENV=check

[codecov-io]

Codecov Report

Merging #37 into master will increase coverage by 6.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #37      +/-   ##
==========================================
+ Coverage   72.12%   78.30%   +6.18%     
==========================================
  Files          11       12       +1     
  Lines         330      424      +94     
==========================================
+ Hits          238      332      +94     
  Misses         92       92              

Impacted Files	Coverage Δ
src/skaero/geometry/coordinates.py	100.00% <100.00%> (ø)

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[aqreed]

fixed this PR, all test ok. @jorgepiloto

[jorgepiloto]

Thank you for the pull request @aqreed and sorry for this late answer. Could you please rebase this branch onto master branch so when merging the git history looks nice?

[aqreed]

@jorgepiloto please tell me if everything is ok