tools: New (safer) option to include additional information blocks into the certificate

The current --subject-info block relies on special formatting of the
input parameters, making it hard to include information that contains
quotes.  The new --signed-info parameter makes minimum assumptions,
treating text before first space as OID and the rest as the associated
string with this OID.

Change-Id: Ic8975f38ed6560be623cf0d2347c69e08fdc9474