Rename circuit_drawer module to drawer

[albi3ro]

circuit_drawer was the only module with an underscore in it, and the circuit part of the name is fairly redundant. What else would we be drawing in PennyLane?

So we are shortening the name to the equally informative drawer.

circuit_drawer contains only developer-facing code. Do we need to import drawer as circuit_drawer as well and raise a UserWarning about the old path?

[codecov]

Codecov Report

Merging #1949 (71530a8) into master (5d01713) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1949   +/-   ##
=======================================
  Coverage   98.81%   98.81%           
=======================================
  Files         225      225           
  Lines       17167    17168    +1     
=======================================
+ Hits        16963    16964    +1     
  Misses        204      204           

Impacted Files	Coverage Δ
pennylane/drawer/__init__.py	100.00% <ø> (ø)
pennylane/drawer/charsets.py	100.00% <ø> (ø)
pennylane/drawer/circuit_drawer.py	100.00% <ø> (ø)
pennylane/drawer/drawable_layers.py	100.00% <ø> (ø)
pennylane/drawer/grid.py	96.77% <ø> (ø)
pennylane/drawer/mpldrawer.py	98.38% <ø> (ø)
pennylane/drawer/representation_resolver.py	99.36% <ø> (ø)
pennylane/drawer/tape_mpl.py	100.00% <ø> (ø)
pennylane/drawer/utils.py	100.00% <ø> (ø)
pennylane/circuit_graph.py	93.88% <100.00%> (ø)
... and 1 more

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[josh146]

Looks good @albi3ro!

circuit_drawer contains only developer-facing code. Do we need to import drawer as circuit_drawer as well and raise a UserWarning about the old path?

Probably not needed, since this module was not user facing.

[josh146]

How come this was changed?

[albi3ro]

While double-checking import paths, I saw qml was only used twice. At that number it's cleaner and more performant to just import directly what we need.