ENH-354 Adding properties to PropertiesComponent

Added setInitialProperties(Properties initialProperties) and getInitialProperties() public methods to PropertiesComponent. These methods allow us to add properties to PropertiesComponent when we can't/won't use external properties (locations).

In SCR bundle, for example, properties are passed to our program as a Map and the only way to get them into PropertiesComponent was setOverrideProperties method. Override properties are however not used if they are the only properties, so we were forced to use a dummy properties file in the bundle.

In addition to the new methods, this pull request changes the override properties handling so that they are always used if they exist (which is the logical thing to do).