Pypuf

* e4839fe: ci: run tests for Python 3.9
* 1ec0e9f: simulation: add/fix inhomogeneous and noisy Feed Forward PUFs
* 51e5f43: ci: adds test suite
* a2d2ae2: metrics: generalize similarity for response values other than {-1,1}

* b28206d: batch: record memory consumption of batch jobs (sample rate 1/s)

* 6f5748a: packages: fix restrictive numpy dependency

* 09c9cd5: ci: run tests, linter on 'main' branch
* 86c2b48: readme: change order of information
* 49abf06: readme/docs: use versionless DOI
* a9f452d: linter: do not complain about unused imports in __init__.py

* e8d03aa: readme: update release instructions
* 78eefed: readme: add information on pypuf v1
* 075f886: metrics: remove approx_ prefix from function names
* 0e5cacf: simulation, metrics: simplify and shorten names
* b305461: simulation: polish Feed Foward Arbiter PUF and add docs
* 6ad9223: simulation: add (XOR) Bistable Ring PUF based on Xu et al. 2015
* f548953: simulation: move LTFArray to base module

* 42169ef: batch: apply randomized order globally
* e10386f: batch: adds method to store study results in memory
* 9129eb7: batch: adds interface to load results
* 32380c7: batch: brush up docs, only use booked number of CPU cores
* cbe2e67: batch: record which values are parameters and wich ones are result
* 017b8bd: batch: enable randomized order in block-wise execution
* 8238ff5: batch: store results in individual files
* f2b90c8: batch: separates storage layer out
* ee9a721: batch: adds callback interface to logging
* 98178c1: batch: enable running a Study without results or log file
* 0d9aa2c: simulation: simplify (un)biased LTF array evaluation