Fromconfig

Added
- The `_attr_` key can be used with an extension name in `Launcher.fromconfig`.

Changed
- The `fromconfig` method of the `FromConfig` base class signature is now generic (`config` does not have to be a Mapping).
- The `Parser` `__call__` signature is also more generic (accepts `Any` instead of `Mapping`)

Deprecated
Removed
- The steps syntax in `Launcher.fromconfig` is now in `DefaultLauncher`

Fixed
- Better type handling for the `OmegaConfParser` (only attempts to find resolvers if `config` is a mapping)

Security

Added
Changed
Deprecated
Removed
- `ReferenceParser`: less powerful than the `OmegaConfParser` but same functionality, only caused confusion.

Fixed
Security

Added
- Improved error message when trying to reload a `.jsonnet` file but `jsonnet` is not installed.
- include `!include` and merge `<<:` support for YAML files
- Custom resolvers easy registration for `OmegaConfParser`
- Default resolver `now` for `OmegaConf`

Changed
- `jsonnet` import does not log an error if jsonnet is not available.

Deprecated
Removed
Fixed
Security

Added
Changed
Deprecated
Removed
Fixed
- docs/README.md must be in data files in setup.py

Security

Added
- `DryLauncher` to dry-run config.
- Skip launcher instantiation if config is `None`

Changed
Deprecated
Removed
Fixed
- Wrong order when merging configs in `cli.main`

Security

Added
- `Launcher` base class with `HParamsLauncher`, `ParserLauncher`, `LoggingLauncher` and `LocalLauncher`
- CLI mechanism for argument parsing and `fire.Fire` integration (now in Launcher)
- Overrides support via key-value parameters for the CLI thanks to `utils.expand`
- `ChainParser` to easily chain parsers.

Changed
- The `FromConfig` class now has a default implementation of `fromconfig`
- The `DefaultParser` now inherits `ChainParser` and its implementation is moved to `parser/default.py`

Deprecated
Removed
- `jsonnet` requirement in the setup.py (it should be optional as it tends to cause issues in some users).

Fixed
Security