added support for loading propertyfiles from http URL

also fixed ORIGINAL.FILE property behaviour. Now when ORIGINAL.FILE is
defined all properties from ORIGINAL.FILE are loaded and then (if defined)
overridden in ReportEngine.properties file defined by
REPORT_ENGINE_PROPERTY_FILE
ORIGINAL.FILE can be now defined either by system property or env variable
(taking precedence before ORIGINAL.FILE property defined in primary file)
Merge pull request #8 from lzoubek/master

Improved handling of ORIGINAL.FILE and loading property files