Added missing JsonFormat::parse() RELEASE NOTES, fixed docs

Constant values were changed to be above 0xFF - this way
we can easily decide to allow depth-parsing-limit to be OR-able:

  FormatJson::parse( $value, 30 | FormatJson::FORCE_ASSOC )

Follows-up Ic0eb0a7 and I1c4f37a.

Change-Id: I9bfd67a5ca4ea1d399821549c7e63ffdecd56ad1