Master should allow to configure truststore access

Current Situation

• The JobScheduler Master makes use of a Java truststore to find public certificates of Agents that it connects to using the HTTPS protocol.
• A number of configuration items are hardwired:
  • the location of the truststore file is ./config/agent-https.jks
  • the type of the truststore is jks
  • the password für the truststore is "jobscheduler"

Desired Behavior

• The above mentioned configuration items should be configurable, i..e. it should be possible to specify the location, type (jks, pkcs12) and password of the truststore with the ./config/private.conf file