Log Message:
Update py-twisted to 10.0.0.
Based on PR#42918 by Wen Heping

Pkgsrc changes:
 * set LICENSE to mit
 * add handling of plugin cache file

Upstream changes:
 from 8.1.0 to 10.0.0 is too long to put here.
 please refer: http://twistedmatrix.com/trac/browser/trunk/NEWS