Mwalib

* Refactored github actions for a more complete CI workflow with automated releases.
* Updated README and install instructions and fixed many markdown issues.

* Modified MWA Legacy read code to produce cotter-compatible visibilities:
* mwalib differs from cotter: cotter produces 0+0j for XY on auto's, mwalib provides the values.
* mwalib and cotter differ from pyuvdata: mwalib/cotter visibilities are conjugated with respect to pyuvdata for cross correlations.
* Added cotter validation data and test to ensure conversion code produces cotter equivalent visibilities (with the above exception).
* Provide rust-fitsio's cfitsio-static feature.
* Bumped fitsio dependency to 0.17.* and changed fitsio-sys to ^0 to ensure fitsio and mwalib use the same fitsio-sys version always.
* Updated CI pipeline: bumped install of cfitsio to v3.49.
* Made error handling code a little lighter.

* Fixed za (zenith angle) calculation.
* Added more comprehensive testing for some coarse_channel methods.
* Addressed many clippy lints.

* Minor updates to enable packaging and deployment to crates.io.
* Fixed visibility of library structs and functions.
* Moved coax_v_factor, mwa_lat_radians, mwa_long_radians and mwa_alt_meters out of metafits_metadata and are now just library constants.

* Major refactoring- this will break compatibility with previous mwalib versions.
* mwalibContext top level object now split into:
* MetafitsContext (when you only provide a metafits file)
* CorrelatorContext (when you provide a metafits and 1 or more gpubox files)
* VoltageContext (when you provide a metafits and 1 or more voltage files)
* FFI interfaces standardised, with struct based functions returning arrays of structs e.g. mwalib_antennas_get returns an array of antennas rather than a single instance.
* Souce code is broken out into seperate folders with their own test.rs unit tests.
* TimeStep struct now has GPS time as well as UNIX time.
* Many new struct members added.
* Many long named members renamed to use shorter or abbreviated names.
* NOTE: VoltageContext does not have data reading functions in this release (however, metadata is supported). This will be added in an upcoming release.

* Added receiver_number and receiver_slot_number to rfinput struct.