Port SelfSignedCertificate from ant-extensions to java-support

Fixed r6484 r6485

Added options for cert algorithm and the subjectAltNames and finished some cleanup.

Should be usable at this point, I'll turn over the Daniel if he wants to figure out a way to use non-deprecated classes or something other than the bcpkix library, which is separate from the bcprov jar.

This is mostly done and working. A main() is also added with command line handling for the basic options needed. I cleaned the code a bit to do better checking of overwriting files, and added the ability to generate any keystore type. PKCS12 seems to work as well as JKS.

Command line options:

$ java -cp "lib/*" net.shibboleth.utilities.java.support.security.SelfSignedCertificateGenerator --help
Usage: SelfSignedCertificateGenerator [options]
Options:
--certfile
Path to certificate file
--help
Display program usage
Default: false
--hostname
Hostname for certificate subject
--keyfile
Path to private key file
--lifetime
Certificate lifetime in years (default: 20)
Default: 20
--size
Size of key to generate (default: 2048)
Default: 2048
--storefile
Path to keystore
--storepass
Password for keystore
--storetype
Type of keystore to generate (default: PKCS12)
Default: PKCS12
--type
Type of key to generate (default: RSA)
Default: RSA