Refactor Web,Scheduler,RM & Portal properties

- To avoid countless duplicated code, all properties have been refactored to use a common helper
- WebProperties and PortalConfiguration has been converted to the existing PASchedulerProperties format
- Proxy configuration properties have been added to WebProperties to allow downloading resources via a proxy
- TrustStore configuration has been added to WebProperties and can be used to include trusted root certificate
- HttpResourceDownloader now takes into account ssl configuration (truststore, allow_any_hostname, etc) when downloading resources in https