xca: initial commit

X - Certificate and Key management

This application is intended for creating and managing X.509
certificates, certificate requests, RSA, DSA and EC private keys,
Smartcards and CRLs.  Everything that is needed for a CA is
implemented.  All CAs can sign sub-CAs recursively. These certificate
chains are shown clearly.  For an easy company-wide use there are
customiseable templates that can be used for certificate or request
generation.

All cryptographic data is stored in a SQL database. SQLite, MySQL
(MariaDB) and PostgreSQL databases are supported.

(brook)