Added rustii CLI command to replace content in a WAD

Also added required library features to make this possible. Rust makes the whole "getting content's index from its CID" thing so much easier.

src/title/content.rs

@@ -110,6 +110,20 @@ impl ContentRegion {
         }
         Ok(buf)
     }
+    
+    /// Gets the index of content using its Content ID.
+    pub fn get_index_from_cid(&self, cid: u32) -> Result<usize, ContentError> {
+        // Use fancy Rust find and map methods to find the index matching the provided CID. Take
+        // that libWiiPy!
+        let content_index = self.content_records.iter()
+            .find(|record| record.content_id == cid)
+            .map(|record| record.index);
+        if let Some(index) = content_index {
+            Ok(index as usize)
+        } else {
+            Err(ContentError::CIDNotFound(cid))
+        }
+    }
 
     /// Gets the encrypted content file from the ContentRegion at the specified index.
     pub fn get_enc_content_by_index(&self, index: usize) -> Result<Vec<u8>, ContentError> {

src/title/mod.rs

@@ -135,8 +135,8 @@ impl Title {
     /// Sets the content at the specified index to the provided decrypted content. This content will
     /// have its size and hash saved into the matching record. Optionally, a new Content ID or
     /// content type can be provided, with the existing values being preserved by default.
-    pub fn set_content(&mut self, content: &[u8], index: usize) -> Result<(), TitleError> {
-        self.content.set_content(content, index, None, None, self.ticket.dec_title_key())?;
+    pub fn set_content(&mut self, content: &[u8], index: usize, cid: Option<u32>, content_type: Option<tmd::ContentType>) -> Result<(), TitleError> {
+        self.content.set_content(content, index, cid, content_type, self.ticket.dec_title_key())?;
         self.tmd.content_records = self.content.content_records.clone();
         Ok(())
     }