Adds amplification models, bumps dependencies, general cleanup

This MR adds new functionality to use the Weatherill et al. (2022) ESRM20 site amplification model to generate maps of mean amplification of ground motion with respect to a user-defined reference site condition (with updated documentation).

Additional changes include:

1. Bug-fix affecting selection of data from hdf5 files when h5py > 3.0 (thanks to Enes Veliu of IUSS Pavia for identifying the bug and proposing the fix)
2. Bump of dependencies (h5py, numpy, pandas) to more recent versions, adds rasterio to dependencies
3. General cleanup of code