[#2217] Feature: Support specifying type for JAAS keystores

[mattrpav]

Sample jaas config blueprint

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:jaas="http://karaf.apache.org/xmlns/jaas/v1.2.0">
  <jaas:keystore name="jmx-truststore.ks"
                 type="PKCS12"
                 rank="1"
                 path="file:etc/truststore.jks"
                 keystorePassword="a..z"/>
  <jaas:keystore name="jmx-keystore.ks"
                 type="PKCS12"
                 rank="2"
                 path="file:etc/keystore.jks"
                 keystorePassword="z...a"
                 keyPasswords="karaf-server.company.com=z..a"/>
</blueprint>