Rename DictPath to DictionaryPath

[mgacy]

• Renames DictPath as DictionaryPath
• Changes parameter names from dictPath to path

New usage:

var dict: [String: Any] = ["outer": ["inner": 5]]

let current = dict[path: "outer.inner"]
dict[path: DictionaryPath("outer.inner")] = 6

Old Usage:

...
let current = dict[dictPath: "outer.inner"]
dict[path: DictPath("outer.inner")] = 6