Remove base plot

[RemDelaporteMathurin]

Fixes #34

Currently, the functions return a module, which is kinda weird... and a new figure is created at each call, making it impossible to make subplots.

Instead, the functions shouldn't return anything (or maybe the current figure via plt.gcf()?).

The workflow would then be:

import regular_mesh_plotter as rmp
import matplotlib.pyplot as plt

rmp.plot_regular_mesh_tally(
    tally=my_tally,
    std_dev_or_tally_value="tally_value",
)
plt.ylabel("my custom Y label")
plt.plot([1, 2, 3], [1, 2, 3])  # add another plot on top of it
plt.savefig('openmc_mesh_tally_plot.png')

A subplot could be created by:

import regular_mesh_plotter as rmp
import matplotlib.pyplot as plt

fig, axs = plt.subplots(nrows=2, ncols=1)

plt.sca(axs[0])  # set first axis active
rmp.plot_regular_mesh_tally(
    tally=my_tally,
    std_dev_or_tally_value="tally_value",
)

plt.sca(axs[1])  # set second axis active
rmp.plot_regular_mesh_tally(
    tally=my_other_tally,
    std_dev_or_tally_value="tally_value",
)

plt.savefig('openmc_mesh_tally_plot.png')

This workflow is more standard

[shimwell]

@RemDelaporteMathurin this failing CI is due to a conda bug that has been reported elsewhere. We could fix the CI by using mamba install. I can do this on a new PR

[shimwell]

Any chance we could branch from develop and merge to develop

[codecov]

Codecov Report

Merging #38 (3b27fbe) into develop (c5293d7) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           develop     #38   +/-   ##
=======================================
  Coverage     0.00%   0.00%           
=======================================
  Files            3       3           
  Lines          136     126   -10     
=======================================
+ Misses         136     126   -10     

Impacted Files	Coverage Δ
regular_mesh_plotter/core.py	0.00% <0.00%> (ø)

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