Add two support functions for building JSON objects
Add two support functions for building JSON objects

The new support functions in module Ganeti.JSON will be used by the next
commits to build JSON objects with optional (Maybe) fields, excluding
them when they contain Nothing.

Signed-off-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

apyrgio/ganeti,apyrgio/ganeti,grnet/snf-ganeti,bitemyapp/ganeti,leshchevds/ganeti,onponomarev/ganeti,leshchevds/ganeti,apyrgio/snf-ganeti,yiannist/ganeti,yiannist/ganeti,andir/ganeti,dimara/ganeti,mbakke/ganeti,bitemyapp/ganeti,onponomarev/ganeti,leshchevds/ganeti,dimara/ganeti,ganeti/ganeti,yiannist/ganeti,andir/ganeti,mbakke/ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1,apyrgio/snf-ganeti,andir/ganeti,grnet/snf-ganeti,mbakke/ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1