Removed APIs for setCorrectionSpan from InputConnection

("setCorrectionSpan" was added in Id3abc9ea4d11753cd )

Also..
- Added a class java doc for CorrectionSpan
- Removed FLAG_DEFAULT
- Changed the return type of getSuggestions from Array<CharSequence> to String[]

Change-Id: If5eb091e307a7a40c5b4a70ec1fe6059ecd9fb2d