add install and remove packages to Backend trait

src/backend/mod.rs

@@ -7,8 +7,14 @@ use crate::Package;
 pub use pacman::Pacman;
 
 pub trait Backend {
+    /// The binary that should be called to run the associated package manager.
+    const BINARY: &'static str;
     /// Get all packages that are installed in the system.
     fn get_all_installed_packages() -> HashSet<Package>;
     /// Get all packages that were installed in the system explicitly.
     fn get_explicitly_installed_packages() -> HashSet<Package>;
+    /// Install the specified packages.
+    fn install_packages(packages: Vec<Package>);
+    /// Remove the specified packages.
+    fn remove_packages(packages: Vec<Package>);
 }