Install contract dependencies from the NFT Catalog

[nvdtf]

Goal

flow contracts install should check and fetch contracts defined in flow.json from the NFT catalog into the imports folder.

• The simple syntax is nft-catalog/NETWORK/COLLECTION_IDENTIFIER e.g. nft-catalog/mainnet/CoolNFT
• Only applies to missing dependencies based on what's inside the imports folder.
• Resolves the contract address using the NFT catalog, then the rest of logic is similar to #944
• imports should be added to .gitignore