Add option to load accounts from file

This introduces the `--clone-from-file` option for
solana-test-validator. It allows specifying any number of files
(without extension) containing account info and data, which will be
loaded at genesis. This is similar to `--bpf-program` for programs
loading.

The files will be searched for in the CWD or in `tests/fixtures`.

Example: `solana-test-validator --clone-from-file SRM_token USD_token`
(cherry picked from commit 9b06d64eb8)

# Conflicts:
#	test-validator/Cargo.toml

cli-output/src/cli_output.rs

@@ -99,7 +99,7 @@ impl OutputFormat {
 pub struct CliAccount {
     #[serde(flatten)]
     pub keyed_account: RpcKeyedAccount,
-    #[serde(skip_serializing)]
+    #[serde(skip_serializing, skip_deserializing)]
     pub use_lamports_unit: bool,
 }