Getter naming conventions

[dralley]

Standard Rust naming convention for getters is to exclude the get_ prefix, e.g.

fn epoch(&self) -> u32;
fn set_epoch(&mut self, epoch: u32);

See: https://rust-lang.github.io/api-guidelines/naming.html#getter-names-follow-rust-convention-c-getter

However in the case of builders (where one doesn't really need to "get" values after setting them) the convention is typically flipped and you set values with methods that are rarely prefixed with set_.

Should we follow these guidelines in the case of Package even though it might potentially be easier to visually confuse with RpmPackageBuilder? (This is Rust, the type information isn't that far away, so it's not that big a deal).

currently methods on Package follow the following pattern (no setters):

fn get_epoch(&self) -> u32;