Split STCN scraping from cleaning (separate modules now).

* [STCN,EXT] Fixed the class membership for the Picarta-scraped STCN data.
* [STCN_CLEAN,NEW] New module, relocated code from module STCN. This module is for scripting the improvement of the data after the Picarta scrape is completed (see module STCN_SCRAPE for that).
* [STCN_GENERIC,EXT] Relocated stcn_graph/1 to this module for better cross-module reuse.
* [STCN_SCRAPE,NEW[ New module, relocated code from module STCN. This module is for scripting the Picarta-based scrape for the STCN.
* [STCN_SCHEMA,SC] Simplified the call to the STCN schema assertion.