Better Qiskit Backends Implementation

[lazyoracle]

What

Under the hood improvements in C3-Qiskit integration

Why

Inheritance helps design more backends easily

How

• Implemented an Abstract Base Class C3QasmSimulator to derive for qasm simulators in C3
• Complete C3QasmPerfectSimulator for non-parametric gates
• Pad gate names and generate gate-names string
• Updated docs and examples with new qiskit interface
• Minor fixes in c3.utils.qt_utils
• Parametric gates implementation pending better naming scheme for parametric gates

[codecov-io]

Codecov Report

Merging #52 (474bac6) into dev (dc99a0d) will decrease coverage by 0.26%.
The diff coverage is 65.08%.

@@            Coverage Diff             @@
##              dev      #52      +/-   ##
==========================================
- Coverage   47.44%   47.18%   -0.27%     
==========================================
  Files          35       35              
  Lines        4542     4593      +51     
==========================================
+ Hits         2155     2167      +12     
- Misses       2387     2426      +39     

Impacted Files	Coverage Δ
c3/utils/qt_utils.py	40.17% <42.85%> (-2.14%)	⬇️
c3/qiskit/c3_backend.py	74.58% <64.75%> (-13.19%)	⬇️
c3/experiment.py	57.07% <75.00%> (-0.41%)	⬇️
c3/qiskit/c3_backend_utils.py	86.48% <85.00%> (+12.12%)	⬆️
c3/qiskit/c3_provider.py	85.29% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dc99a0d...474bac6. Read the comment docs.