Adds the `corso restore` command to the cli (which only displays
a help menu). And adds the `corso restore exchange`
command (which also only displays a help menu) to the cli.
Further functionality (like the complete flags) will come later.
Adds unit tests for the config file read/write helpers.
It also uncovered a bug in how viper handles writing a config file when a config file path is set
directly. This required a workaround in our init logic when we are using a custom config file name.
This commit does the following:
- Refactors the init logic into a InitConfig helper
- Adds a unit test to validate basic ReadRepoConfig behavior
- Adds a unit test that uses WriteReadConfig to write config and ReadRepoConfig to read it
