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ARROW-4827: [C++] Implement benchmark comparison

This script/library allows comparing revisions/builds.

Author: François Saint-Jacques <fsaintjacques@gmail.com>

Closes #4141 from fsaintjacques/ARROW-4827-benchmark-comparison and squashes the following commits:

a047ae4ed <François Saint-Jacques> Satisfy flake8
e95baf317 <François Saint-Jacques> Add comments and move stuff
ee39a1feb <François Saint-Jacques> Move cpp_runner_from_rev_or_path in CppRunner
2a953f180 <François Saint-Jacques> Missing files
d8e3c1c85 <François Saint-Jacques> Review
514e8e428 <François Saint-Jacques> Introduce RegressionSetArgs
280c93be4 <François Saint-Jacques> Update gitignore
dc031bde7 <François Saint-Jacques> Support conda toolchain
28254676c <François Saint-Jacques> Add --cmake-extras to benchmark-diff command
e6762899c <François Saint-Jacques> Typo
048ba0ede <François Saint-Jacques> Add verbose_third_party
71b10e98a <François Saint-Jacques> Disable python in benchmarks
c3719214c <François Saint-Jacques> Fix flake8 warnings
8845e3e78 <François Saint-Jacques> Remove empty __init__.py
1949f749c <François Saint-Jacques> Supports HEAD revisions
96f999748 <François Saint-Jacques> Add gitignore entry
d9692bc8f <François Saint-Jacques> Fix splitlines
90578af61 <François Saint-Jacques> Add --cmake-extras to build command
7696202ba <François Saint-Jacques> Add doc for bin attribute.
a281ae8e6 <François Saint-Jacques> Various language fixes
1b028390c <François Saint-Jacques> Rename --cxx_flags to --cxx-flags
bc111b2d3 <François Saint-Jacques> Removes copied stuff
d6733b6f4 <François Saint-Jacques> Formatting
21b2e14fc <François Saint-Jacques> Add doc and fix bugs
2a81744cf <François Saint-Jacques> Ooops.
c85661cf3 <François Saint-Jacques> Add documentation
703cf987a <François Saint-Jacques> commit
2c0d512f8 <François Saint-Jacques> Checkpoint
a38f49cd9 <François Saint-Jacques> checkpoint
a5ad76d11 <François Saint-Jacques> Fix syntax
712d2ed3c <François Saint-Jacques> initial commit