Write `get-file` and commands to get the list of blocks from another node

Description

This closes #1 (closed) by providing an API that allows to get a file with just its hash

Detailed list of changes

• add get_file, get_blocks_info_from and other things related to managing the filesystem
• add new commands to nu API
• remove DragoonBehaviour as it was not useful
• add two new tests for get_file and change the already existing test to use the new API

Note

The get_file is still very rough, the error management needs to be handled better to take into a lot more cases of failure

src/to_serialize.rs

@@ -13,9 +13,10 @@ pub(crate) trait ConvertSer {
     fn convert_ser(&self) -> impl Serialize;
 }
 
-/// Used to implement for all types that are already Serialize and only need to return self (kind of a default implementatioon basically)
+/// Used to implement for all types that are already Serialize and only need to return self (kind of a default implementatioon basically).
 /// We do not directly implement for all Serialize, because it is a foreign trait and could lead to double implementation conflicts later on if PeerID decided to implement Serialize for example
-/// Macro rule taken from: https://stackoverflow.com/a/50223259
+/// 
+/// Macro rule taken from: <https://stackoverflow.com/a/50223259>
 macro_rules! impl_Convert {
     (for $($t:ty),+) => {
         $(impl ConvertSer for $t {