refactor modules, layout

This PR would merge the following "major" changes into main:

switch from using setup.py to pyproject.toml, in line with this recommendation, (#29)
switch to using a "src" layout, in line with this recommendation
re-factor + re-organize modules and functions
remove bash scripts, replaced by entry points (for cross-platform use) (#30)

code changes

The following is a short summary of the changes made to the different modules.

spymicmac.data:

spymicmac.matching:

move matching-related functions, including fiducial template and gcp matching, from spymicmac.image
small formatting tweaks to docstrings

spymicmac.micmac:

rename run_bascule and run_campari to bascule and campari, respectively
move orientation-related functions to spymicmac.orientation
add post_process, replacing the old shell script post_process_micmac.sh
add get_autogcp_locations, replacing the old shell script get_autogcp_locations.sh
small formatting tweaks to docstrings

spymicmac.orientation:

move orientation-related functions from spymicmac.micmac and spymicmac.register
small formatting tweaks to docstrings

spymicmac.resample:

moved downsample, resample_hex, rotate_kh4, and resample_kh4 from spymicmac.image
small formatting tweaks to docstrings

spymicmac.register:

spymicmac.tools:

add block_orientation, for combining orientation blocks into a single orientation
add post_process_micmac, replacing previous bash script
small formatting tweaks to docstrings