No example to use libpisp

[gregoiregentil]

There is no simple example how to use libpisp. The closest I found is this code.

It would be good to have a simple example how to configure the pisp-fe via this library.

[naushir]

Sorry for taking so long with this. I've attempted to add some helpers and an example convert command line application using a few features of libpisp here: #35. I do plan on extending this for DNG/RAW files, but no timeline on that yet.

[naushir]

#35 has now been merged.