DVC: Data Version Control - Git for Data & Models

Refer to https://dvc.org/doc/install for installation instructions.

• Support for WebHDFS (#4747) @tomasfarias
• 4504: configuration-based job limit. (#4872) @I159
• utils/fs: checking files ownership in 'move' (#4348) (#4832) @danielfleischer
• Simpler param updates with python-benedict (#4780) @sjawhar
• add: support simple wildcards (#4864) @ju0gri
• experiments: add dvc exp gc (#4803) @pmrowla
• dvc: add size/nfiles for deps/outs (#4836) @efiop
• Plots: Better confusion matrix, and normalized version to (#4775) @sjawhar
• import: add --no-exec param (#4817) @BurnzZ
• command: add dvc push instruction after dvc repro (#4737) @jvfe
• metrics/plots: test metrics collection on no target on revision (#4789) @pared
• dag: add --outs option (#4739) @JIoJIaJIu

• git: use dulwich for .gitignore (#4809) @efiop

• remote: avoid chunking on webdav. Fixes #4796 (#4828) @LucaButera
• [#4136] fixed recalculating relative paths in config (#4802) @godfryd
• plots: fix plots path when calling from different dir (#4843) @pared
• http: raise error on unsuccessful http statuses on exists (#4785) @damakuno
• diff: handle empty output status (#4826) @pmrowla
• [#4819] fixed failing to push some files to http remote (#4820) @simonlousky
• add: warn on cache link errors instead of failing (#4801) @pmrowla
• metrics/plots: test metrics collection on no target on revision (#4789) @pared

• ci: add macos-11 @ py3.8, py3.9 to build matrix (#4892) @pmrowla
• cache: refactor cache types (#4866) @efiop
• dvc: use DirInfo instead of dicts/lists (#4851) @efiop
• cache: refactor dir_info conversion (#4844) @efiop
• build: test built binary (#4839) @efiop
• pyarrow: upgrade to 2.0.0 (#4795) @efiop

Thanks again to @BurnzZ, @I159, @JIoJIaJIu, @LucaButera, @damakuno, @danielfleischer, @efiop, @godfryd, @ju0gri, @jvfe, @pared, @pmrowla, @simonlousky, @sjawhar, @skshetry and @tomasfarias for the contributions! 🎉