Fix Instructions ideal gate assignment in constructor

[YonatanGideoni]

What

Makes the Instruction class properly assign ideal gate inside constructor. Also fixes the two_qubits_entangling_gate.ipynb example notebook.

Why

Closes #229

How

Added self.set_ideal(ideal) to Instructions constructor.

Remarks

None

Checklist

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• [x] Tests - A new test was created, manually made sure that it gives the required output on a simple test case and that it does not break some existing code.
• [x] Formatting & Linting - black has been used to ensure styling guidelines are met
• [x] Type Annotations - All new code has been type annotated in the function signatures using type hints
• [x] Docstrings - Docstrings have been provided for functions in the numpydoc style
• [x] Documentation - The tutorial style documentation has been updated to explain changes & new features. No changes were required.
• [x] Notebooks - Example notebooks have been updated to incorporate changes and new features
• [x] Changelog - A short note on this PR has been added to the Upcoming Release section

[CLAassistant]

All committers have signed the CLA.

[codecov[bot]]

Codecov Report

Merging #230 (fd79d3b) into dev (01cd657) will increase coverage by 0.02%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #230      +/-   ##
==========================================
+ Coverage   74.82%   74.85%   +0.02%     
==========================================
  Files          38       38              
  Lines        5534     5535       +1     
==========================================
+ Hits         4141     4143       +2     
+ Misses       1393     1392       -1     

Impacted Files	Coverage Δ
c3/signal/gates.py	95.60% <100.00%> (+0.57%)	:arrow_up:

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[YonatanGideoni]

Review was dismissed by Github because of conflict resolution, nothing important changed.

[lazyoracle]

@YonatanGideoni Setup the pre-commit hooks as described in the CONTRIBUTING document so that all commits are blacked and linted by default.