Added retry-option to work around occasional failure while checking out git repo due to race condition.

Removed unnecessary unsafe blocks and fixed a bug related to adding invalid sample values to `Utilized` random variables.

Minor changes to the README, changed dependencies to ODEM-rs crates in Cargo.toml to be able to develop them independently.

Profiled and improved performance of the event calendar. Made it private in order not to commit to early.

Reworked the `uom` integration: namespaces for all quantities and an extension trait for easier unit construction. Quantities are pushed into a separate macro for easier updating to later versions of `uom`.

Made the derive for `Config` rely on the definition of `DefaultConfig` in core, rather than just assuming its `(f64, (), ())`. This allows changing it later without having to touch the meta crate.

Cleaned up the root module of the library to prevent the IDE from suggesting private `use` directives in user projects.