Moving utility functions to a utils package

[antalszava]

Context: As further additions would extend the utils module (e.g. functions for post-processing of samples) it became desirable to make is a package.

Description of the Change: Creates a new utils package and imports names from the utils module.

Benefits:

• The utils package can be further extended
• There are no breaking changes for user code that use gates from utils

Possible Drawbacks: Importing names from utils.py requires managing a long list for __all__. The alternative of resorting to an absolute import would, however, this would both introduce discrepancies in the test suite as well as potentially break user code.

Related GitHub Issues: Related PR: #399

[codecov[bot]]

Codecov Report

Merging #413 into master will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #413   +/-   ##
=======================================
  Coverage   97.84%   97.84%           
=======================================
  Files          59       63    +4     
  Lines        6760     6774   +14     
=======================================
+ Hits         6614     6628   +14     
  Misses        146      146           

Impacted Files	Coverage Δ
strawberryfields/utils/__init__.py	100.00% <100.00%> (ø)
strawberryfields/utils/decorators.py	100.00% <100.00%> (ø)
strawberryfields/utils/program_functions.py	97.77% <100.00%> (ø)
strawberryfields/utils/random_numbers_matrices.py	100.00% <100.00%> (ø)
strawberryfields/utils/states.py	100.00% <100.00%> (ø)

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