Evaluate consistency and naming of char vs u32 methods in icu_collections and icu_properties

[sffc]

We inconsistently name methods in the various properties and collections classes that deal with char vs u32. Examples: contains(char), contains_32(u32), get(char), and get_u32(u32), but sometimes it is get(u32). And the get_u32 name sounds like it is returning a u32, similar to get_ule, when in fact it is an overload of the get method.

Feedback from @markusicu.

Thoughts?

• [ ] @echeran
• [ ] @Manishearth