Translate: Allow locale-specific rules

[Nao]

When I review translations of others (especially new contributors), I often find myself spending time correcting & telling about the same issues that are against the rules in ​our style guide.

Here are some examples:

Warning (if these are violated, the translation should never be approved)

1. Never use multibyte symbols and numbers such as: １,？,！,％,＄
2. Use hiragana instead of kanji for "全て" (= all), "下さい" (= please)

Notice (there are some exceptions so the translator needs to confirm that it's not against the rule)

1. In most cases, try to omit the word "you (あなた)"
2. Place a single-byte space before & after an alphabetic word/phrase, unless it's right next to one of the following: 。,、,:,(,) etc...

I'm sure there are similar types of (relatively) minor but style-violating mistakes that often come up for each locale. Correcting these are very mind-numbing for editors, but at the same time, it's not very easy for new contributors to understand all these rules in the first place.

I think it's best if GlotPress can automatically handle these kinds of warnings and notices so editors can spend more time on other things.