Multiple calls of e.g. CreateString inside a call to a CreateTable
could cause those strings to end up in different locations in the
wire format, since order or argument evaluation is undefined.

This is allowed by the FlatBuffer format, but it is not helpful,
especially when debugging the contents of binaries, or comparing
against a "golden" binary for tests etc.

Now making sure that all the CreateTableDirect calls first serialize
sub strings/vectors before calling CreateTable.

Also made similar changes to the serialization of "binary schemas".

Change-Id: I5747c4038b37a0d400aca2bc592bec751cf5c172