Better wrapping with Rust

Trying to hide most of the CXX nastiness behind the actual module
Move the CXX ffi stuff to its own module
Separate mgr and module mods
Modify main.rs to use the basic code we have done so far

src/main.rs

@@ -1,6 +1,10 @@
-use sword_rs::mgr::{new_mgr, Mgr};
+use sword_rs::mgr::Mgr;
 
 fn main() {
-    let mgr = new_mgr();
-    println!("{:?}", mgr.get_modules());
+    let mut mgr = Mgr::new();
+    for mod_name in mgr.get_modules() {
+        let mut module = mgr.get_module(&mod_name);
+        println!("Module: {}", module.get_name());
+        println!("Text: {}", module.strip_text());
+    }
 }