Add ShellOption, DeletedWrapper

Abstracts away option writing such that users no longer have to
understand scopt semantics. This adds a ShellOption class and a
HasShellOptions trait for something which provides one or more
ShellOptions. This refactors the FIRRTL codebase to use this style of
option specification.

Adds and uses DeletedWrapper to automatically generate
DeletedAnnotations.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>