Hybrid Schrödinger-Feynman Simulation Preparation

[burgholzer]

This PR adds the essential functionality to the JKQ DD Package to support hybrid Schrödinger-Feynman simulation.
The main change is that decision diagrams might now "start" (from the bottom) with a different qubit than 0, which is needed for splitting the circuit horizontally.
Additionally, this PR adds functionality that allows to efficiently export a complete set of amplitudes from a state vector DD and to transfer an existing DD to another package instance.

✨ state generation, matrix generation, and multiplication receive an additional parameter start (default 0) that indicates the bottom-most qubit the DD is built from
💥 removed the makeGateDD constructor taking two Qubit arguments for control and target, as it is ambiguous with the new start parameter
✨ method for deleting a specific edge of a DD node
✨ kronecker receives an additional parameter indicating whether to increase the indices of the top DD
✨ method for tranfering a DD Edge from one package to another
✨ methods for (recursively) exporting and adding amplitudes
✨ ComplexValue addition
🏁 fix binary serialization issues under Windows
♻️ runtime exceptions instead of assertions
📝 fix readme example
📄 updated license

[codecov]

Codecov Report

Merging #12 (79c0af3) into master (9a98015) will decrease coverage by 0.0%.
The diff coverage is 98.6%.

@@           Coverage Diff            @@
##           master     #12     +/-   ##
========================================
- Coverage    95.4%   95.3%   -0.1%     
========================================
  Files          17      17             
  Lines        2274    2290     +16     
========================================
+ Hits         2170    2184     +14     
- Misses        104     106      +2     

Impacted Files	Coverage Δ
include/dd/ComplexValue.hpp	97.0% <ø> (ø)
include/dd/Package.hpp	92.5% <98.3%> (-0.1%)	⬇️
include/dd/Export.hpp	93.5% <100.0%> (ø)
test/test_complex.cpp	100.0% <100.0%> (ø)
test/test_package.cpp	100.0% <100.0%> (ø)

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[hillmich]

Nicely done.