Explicitly send ICS files in UTF-8.

- In memory attachments are now stored as byte[], not String.
  We can store any type of contents now.
- Added blob content_bytes to the Attachment table.
  The content field is now deprecated and not used.
- Explicitly convert ICS files to UTF-8.

- Added Utility.to/fromUtf8().

Bug 2509287
Change-Id: I3785a365a9a34039ec12ba82bd857dcdbc4de92d
2 files changed