JobScheduler Master authenticates itself to Universal Agent

Desired Behavior

• When accessed via HTTPS, the Universal Agent requires authentication (JS-1631). The JobScheduler Master authenticates itself with its Scheduler ID and the password fetched from config/private/private.conf, entry jobscheduler.master.credentials.password, for example

  jobscheduler.master.credentials.password = "my secret password for agents"
  

• TLS certicates from unknown Certification Authorities (CA) are supported. The trusted certificates can be placed in an optional Java keystore file config/agent-https.jks. A keystore requires password, which is expected to be "jobscheduler".