Add EF launchpad import (#1381)

## Issue Addressed

NA

## Proposed Changes

Adds an integration for keys generated via https://github.com/ethereum/eth2.0-deposit (In reality keys are *actually* generated here: https://github.com/ethereum/eth2.0-deposit-cli).

## Additional Info

NA

## TODO

- [x] Docs
- [x] Tests

Co-authored-by: Michael Sproul <michael@sigmaprime.io>

account_manager/src/validator/mod.rs

@@ -1,5 +1,6 @@
 pub mod create;
 pub mod deposit;
+pub mod import;
 pub mod list;
 
 use crate::common::base_wallet_dir;
@@ -21,6 +22,7 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
         )
         .subcommand(create::cli_app())
         .subcommand(deposit::cli_app())
+        .subcommand(import::cli_app())
         .subcommand(list::cli_app())
 }
 
@@ -30,6 +32,7 @@ pub fn cli_run<T: EthSpec>(matches: &ArgMatches, env: Environment<T>) -> Result<
     match matches.subcommand() {
         (create::CMD, Some(matches)) => create::cli_run::<T>(matches, env, base_wallet_dir),
         (deposit::CMD, Some(matches)) => deposit::cli_run::<T>(matches, env),
+        (import::CMD, Some(matches)) => import::cli_run(matches),
         (list::CMD, Some(matches)) => list::cli_run(matches),
         (unknown, _) => Err(format!(
             "{} does not have a {} command. See --help",