Make platform_channels_swift use more idiomatic Swift
* Remove semicolons.
* `if (condition)` => `if condition`.
* `Class.init(...)` => `Class(...)`.
* Remove `break` statements from `switch` cases.
* Remove some unnecessary uses of `self`.
* wip
* wip
* delete main.m
* readd main.m
* update to use new channel api
* update android
* removed android/
* remove debug print
* remomved main.m
* Update year in copyright
* break long line and update name
* mit comments
* update examples/README
* break line
* update README
* update test
