Implement fine-grained file cache control options

[pjbull]

Implements fine-grained controls for file cache clearing.

Best overview is the update to caching.ipynb, which you can see in the docs preview:
https://deploy-preview-314--gallant-agnesi-5f7bb3.netlify.app/caching/#clearing-the-file-cache

Probably worth it to start with reading the docs since we want those to be a clear explanation of the change.

Bonus:

• Our file closing was not idempotent (if .close() was called twice, the file would upload twice). This usually resulted in a failure to overwrite because modified times were the same. Fixed to not upload if close has already been called.
• Hide input/output numbers in docs generated by jupyter notebooks

Closes #10

[github-actions]

🚀 Deployed on https://deploy-preview-314--gallant-agnesi-5f7bb3.netlify.app

[codecov-commenter]

Codecov Report

Merging #314 (2e0b336) into master (bb9d0a3) will decrease coverage by 0.2%.
The diff coverage is 97.5%.

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Additional details and impacted files

@@           Coverage Diff            @@
##           master    #314     +/-   ##
========================================
- Coverage    94.2%   94.1%   -0.2%     
========================================
  Files          21      22      +1     
  Lines        1396    1461     +65     
========================================
+ Hits         1316    1375     +59     
- Misses         80      86      +6     

Impacted Files	Coverage Δ
cloudpathlib/client.py	89.1% <92.5%> (+1.2%)	⬆️
cloudpathlib/azure/azblobclient.py	93.9% <100.0%> (+<0.1%)	⬆️
cloudpathlib/cloudpath.py	92.8% <100.0%> (+0.2%)	⬆️
cloudpathlib/enums.py	100.0% <100.0%> (ø)
cloudpathlib/exceptions.py	100.0% <100.0%> (ø)
cloudpathlib/gs/gsclient.py	92.8% <100.0%> (-1.6%)	⬇️
cloudpathlib/local/localclient.py	96.6% <100.0%> (+<0.1%)	⬆️
cloudpathlib/s3/s3client.py	92.4% <100.0%> (-1.5%)	⬇️

[jayqi]

This looks awesome! Will be a great new feature.

I saw a bunch of typos in the caching notebook—wondering if we should nbautoexport it for PR review purposes.

[pjbull]

@jayqi Should be ready for re-review, sorry had to rebase. New commits are from 6180bdb onwards. You can probably ignore c121e65, which is just running black on the notebooks.

[pjbull]

Thanks @jayqi! I incorporated all your suggestions

[jayqi]

One remaining typo. LGTM otherwise!