Refactoring particleset creation method

[michaeldenes]

This PR is to change the particleset creation method, splitting it into two parts. One method allows users to create a particle set using one of the predefined initialisation maps, and the other method allows users to pass in their own release locations and plastic amounts.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.76923% with 5 lines in your changes missing coverage. Please review.

Project coverage is 66.24%. Comparing base (5269406) to head (b195ac3).

Files	Patch %	Lines
plasticparcels/constructors.py	80.76%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
- Coverage   67.60%   66.24%   -1.37%     
==========================================
  Files           8        8              
  Lines         744      705      -39     
==========================================
- Hits          503      467      -36     
+ Misses        241      238       -3     

Flag	Coverage Δ
unit-tests	66.24% <80.76%> (-1.37%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[erikvansebille]

This branch is now set to merge into master, but also includes adding_new_tests. Should it not merge into that second branch? Or should adding_new_tests not first be merged into master?

[michaeldenes]

This branch is now set to merge into master, but also includes adding_new_tests. Should it not merge into that second branch? Or should adding_new_tests not first be merged into master?

I want to PR adding_new_tests first, then this one. I merged adding_new_tests into this branch so I could run the pytests. So we can merge that first, then this one.

[erikvansebille]

This branch is now set to merge into master, but also includes adding_new_tests. Should it not merge into that second branch? Or should adding_new_tests not first be merged into master?

I want to PR adding_new_tests first, then this one. I merged adding_new_tests into this branch so I could run the pytests. So we can merge that first, then this one.

Yes, that would help me with reviewing, because now I will need to also go through all the changes of the adding_new_tests branch in https://github.com/OceanParcels/plasticparcels/pull/39/files