Extractor class should allow custom extensions

[locked-fg]

The Extractor class currently only supports FeatureDescriptor s that live in the
de.lmu.ifi.dbs.jfeaturelib.features
package (or below).

It should support third-party packages, too, as long as they implement the desired interface.

It should also support the output file name "-" to output to stdout. There is a spelling error in the java source:

"cretae the output"

[locked-fg]

Finding all classes that implement a certain interface is a general problem due to the possibility of having multiple class loaders.

Currently I do not know an easy way to add this functionality in an easy way.

As the Extractor is "just" a convenient tool to simplify the extraction of the features. It will probably not be solved in this place.

I'm thinking about it but will possibly close the issue.

[locked-fg]

https://code.google.com/p/reflections/
Might be a solution. Nevertheless I still don't like the idea of walking the complete classpath (and loading each and every class)