Shepherd-data

- add zstd-compression for embedded fw
- derive fw-name if not provided
- only mock uninstalled modules / packages
- speedup on BBone from 47 s to ~10 s
- hash-default-value in user-model took 25 s
- loading fixtures took 6 s (now pickled on first use)
- scipy.stats takes 4.4 s to import in cal_measurement
- requests takes 1.3 s to import in testbed_client
- next slowest external module are: numpy 1.5 s, pwnlib.elf 1.4 s

- ELF-support by default

- add and use fw-helper-fn: compare_hash(), base64_to_hash()
- allow to generate fw-mod from fw-model
- cleanup import-system for pwntools (dependencies caused trouble on windows & BBone)

- improve handling of uninstalled submodules (elf, inventory)
- add helper FNs for fw_tools, including utests
- fix missing imports
- add hash to fw-model

- fix missing imports
- better handle uninstalled sub-modules

- add inventory-functionality
- add uart-waveform decoder
- improve codequality & extend unittests
- update dependencies
- add this changelog