Cleaning up objects, stating requirements explicitely.

I have cleaned up the objects, and stated all requirements explicitely .

My next step is to get rid of the dependency on [shell], but that will have to wait until I have released PuREST JSON 1.0.0, as this version will include some breaking changes, to keep it consistent with other Pd objects and libraries.

I have also removed the load and preview part from [fs_content_search], because neither [fs_text_search] nor [fs_similar] include this functionality.