Add 2D and 3D grid positions

[marjanalbooyeh]

This PR adds the following functions to the geometry file:

1. radial_grid_positions: returns a radial grid of 2D positions between two radii. Number of circles between the two radii, number of points in each circle and the coverage angle of each circle can be customized.

2. spherical_grid_positions: returns a spherical grid of 3D positions between two radii and an angle along z axis. Number of circles between the two radii, number of points in each circle and the coverage angle of each circle can be customized.

These functions can be useful when a fixed set of positions needs to be swipped in a simulation.

[chrisjonesBSU]

Thanks for adding these :)

A couple things:

1. It looks like we need to pin the gsd version to 2.9 in the environment file. We can update the gsd stuff in a separate PR.

2. For consistency, can you follow the same format used in the rest of the cmeutils code in terms limiting lines to 80 characters if possible, and passing funciton args to individual lines once past 80 characters? I think this PEP8 guide covers that Maybe at some point we can add the precommit CI tool that automatically makes these PEP8 related changes to this repo.

3. Similar to 2, I think we should follow a consistent format in the doc strings where the first line shows the paramter name, data type, and default values, and a second indented line gives the parameter description.

[chrisjonesBSU]

Looks like the rigid body related tests are failing. We should probably pin hoomd < 4.0.

Per the hoomd 4 release notes:

hoomd.md.constrain.Rigid no longer takes diameters or charges as keys in the body parameters.

[codecov]

Codecov Report

Merging #48 (eb27b30) into master (3486480) will decrease coverage by 3.53%.
Report is 1 commits behind head on master.
The diff coverage is 96.61%.

❗ Current head eb27b30 differs from pull request most recent head 51ecda1. Consider uploading reports for the commit 51ecda1 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
- Coverage   99.07%   95.54%   -3.53%     
==========================================
  Files           7        7              
  Lines         431      449      +18     
==========================================
+ Hits          427      429       +2     
- Misses          4       20      +16     

Files Changed	Coverage Δ
cmeutils/dynamics.py	96.00% <0.00%> (ø)
cmeutils/gsd_utils.py	86.04% <91.66%> (-12.41%)	⬇️
cmeutils/geometry.py	98.27% <100.00%> (+0.77%)	⬆️
cmeutils/plotting.py	100.00% <100.00%> (ø)
cmeutils/sampling.py	100.00% <100.00%> (ø)
cmeutils/structure.py	100.00% <100.00%> (ø)

[chrisjonesBSU]

LGTM! Thanks for adding this @marjanAlbouye