Adjust the structure of tools directory and rename some scripts

[dreamerlin]

This PR adjusts the tools directory structure and rename some scripts files.

1. anet_feature_prepare.py -> activitynet_feature_extraction.py, gen_flow.py -> flow_extraction.py, tsn_feature_extract.py -> tsn_feature_extraction.py
2. Create tools/analysis directory and put analyze_logs.py, bench_processing.py, benchmark.py, get_flops.py and report_accuracy.py into it.
3. Put activitynet_feature_extraction.py and tsn_feature_extraction.py in tools/data/activitynet
4. Update the docs.

[codecov]

Codecov Report

Merging #142 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #142   +/-   ##
=======================================
  Coverage   84.21%   84.21%           
=======================================
  Files          73       73           
  Lines        4175     4175           
  Branches      638      638           
=======================================
  Hits         3516     3516           
  Misses        554      554           
  Partials      105      105           

Flag	Coverage Δ
#unittests	84.21% <ø> (ø)

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Impacted Files	Coverage Δ
mmaction/models/recognizers/recognizer2d.py	78.57% <ø> (ø)
mmaction/models/recognizers/recognizer3d.py	81.81% <ø> (ø)

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[innerlee]

the term generation is no better than extraction. generation is an ML task such as GAN, while extraction is a technical operation for feature extraction.

edit: feature_preparation is more accurate than extraction, what do u think? also, they belong to the tools/data right?

[dreamerlin]

the term generation is no better than extraction. generation is an ML task such as GAN, while extraction is a technical operation for feature extraction.

edit: feature_preparation is more accurate than extraction, what do u think? also, they belong to the tools/data right?

generation -> extraction. Move activitynet_feature_extraction.py to tools/data/activitynet