Allow defining full path to Git repository for components

[simu]

Enable Commodore to use components which are hosted in different repositories. This will likely require some reworking of the current component discovery mechanism, which relies on the COMMODORE_GLOBAL_GIT_BASE configuration to actually clone component repositories.

Task deliverables

• Commodore can clone components hosted on different Git services
• A Git base URL is configured as a default for components
• Overrides can be specified for single components in the config file (commodore.yml)
• In addition, component_versions can be used to change the URL for a component in the hierarchy

[srueg]

As discussed, I'll write the SDD with the following idea:

1. A Git base URL is still configured as a default for components ✔️
2. Overrides can be specified for single components in the config file (same as in Make the Inventory Structure Configurable #93) ✔️
3. In addition, component_versions can be used to change the URL for a component in the hierarchy (only in addition to the global config though).