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/dragoon_network.rs

@@ -882,6 +882,7 @@ where
                         let number_of_blocks_to_reconstruct_file = block.shard.k;
                         debug!("Number of blocks to reconstruct file {} : {}", file_hash, number_of_blocks_to_reconstruct_file);
                         if verify::<F,G,P>(&block, &powers)? {
+                            //TODO check if the new block is not linearly dependant with the other blocks already on disk
                             debug!("Block {} for file {} was verified successfully; Now dumping to disk", block_response.block_hash, file_hash);
                             let _ = fs::dump(&block, &block_dir, None, Compress::Yes)?;
                             number_of_blocks_written += 1;