--unicode (-u) and --encoding flags

[ExpHP]

The resolution to #2 so far is a bit complete; as of right now, binary files always use Shift-JIS strings, when the intent was to let them use any ASCII-compatible encoding.

I have a git stash where I tried to add these flags, but something bothered me about it: In particular, I was forced to thread a &'static Encoding parameter through many functions in src/formats/{anm,msg,std}.rs.

The most annoying part is the fact that both (de-)compilation (i.e. AnmFile <-> ast::Script) AND file IO (i.e. fn(&AnmFile, &mut BinWrite) functions require the argument:

• File IO functions require it because types like AnmFile contain Strings.
• Compilation/decompilation requires it because the current LLIR instr type contains a fully encoded blob of argument bytes

I think it's better to eliminate the first bullet; AnmFile should contain Encoded for its strings. The only annoying part then is that the Meta conversions will require the encoding.