core: fix ubf encoding of objects. Does this fix #804?
mod_admin: Fix propagate rsc update error messages to the frontend

m_rsc:update uses `throw` for error validation whereas
controller_admin_edit assumed it used {error, ..} return values.
core: Explicitly annotate binaries with > 127 code points as UTF-8
core: Use conditional compilation for UTF-8 literals

Also remove the use of some curly quotes in the .erl files to keep the
conditional defines to a minimum.

Fixes #804

See https://github.com/zotonic/zotonic/issues/804#issuecomment-54030040