Dvc

* plots: add smooth template (4046) pared

* plots: make sure template is using data anchor (4045) efiop
* plots: modify: handle --unset for nonexistent options (4044) efiop
* remote: continue remote/cache/tree refactoring (4041) pmrowla
* Performance improvement of dvcignore (3967) karajan1001

* (bugfix) get/import: fix broken progress bar (4039) skshetry
* metrics & plots: help output improvements (3963) nik123
* gdrive: add open (3916) casperdcl
* snap: make future major version upgrades easier (4038) casperdcl

* run: maintain order when -f/--force overwrite stage (4035) skshetry
* metrics: diff: introduce --precision (4026) efiop
* fix error message on dag.py (4036) skshetry
* bugfix: `get` dump folder contents in respective output folder (4034) skshetry
* schema: provide a jsonschema for dvc.yaml (4028) skshetry
* plots: fix handling of multiple plots from single revision (4031) pared
* tests: unittests for dvcfile and some small fixes (4032) skshetry
* remote: separate cloud remote and cloud cache classes (4019) pmrowla
* remote: use separate working tree instance for local cache (3991) pmrowla
* 4021, do not make config directory world writeable (4022) bjonnh

* tests: cover run cache with functional tests (4018) skshetry
* plots: fix a couple of bugs (4017) Suor
* RepoTree: work with dirty repos (4005) efiop
* run: use -f/--force to overwrite, fix msg (4011) skshetry
* plots modify: do not convert output types to plot on unset (4009) skshetry
* dvc.yaml: preserve meta (4008) skshetry
* plots modify: complain if template does not exist (3995) skshetry
* add/run/import-url: don't use -f as --file (4004) efiop
* plots: rename --no-csv-header to --no-header (4001) efiop
* config/remote/cache: make --system/--global/--local mutually exclusive (4000) efiop
* status: introduce --show-json (3998) efiop
* snap: build fixes (3990) casperdcl
* Refactor plots (3994) Suor
* plots: find metric data in yaml dictionary (3992) pared
* stage: don't consider stage as cached if checksum/cmd changed (3993) skshetry
* tests serializing of stage to lockfile (3988) skshetry
* tests: serialize pipeline file (3985) skshetry
* plots: fix help message (3983) efiop
* remove unnecessary dependencies (3987) skshetry
* tests: update mock ssh server (3986) skshetry
* remote: tree: don't ignore exceptions (3977) efiop
* log: show modifying if entry already exists in dvcfile (3978) skshetry
* tests: StageLoader for Pipeline file stages (3976) skshetry
* issue template: do not auto-add labels on new issues (3979) skshetry
* Fix loading of params from run cache (3972) skshetry

* pyinstaller: add hook for google-api-python-client (3965) efiop
* snap: restrict site-package checks (3878) casperdcl
* Subcommand help (3956) aerubanov
* remote: fix remaining gdrive build issues (3959) pmrowla
* remote: fix build errors (3957) pmrowla
* refactor/test multistage load for params and outputs (3949) skshetry
* Unify metrics behavior with dirs (3935) nik123
* remote: finish separating RemoteTree methods (3946) pmrowla