[NT] Doc - content_file_decoder.
[NT] Doc - task server p. 1
[NT] Doc - task server p. 2
Merge remote-tracking branch 'origin/master'

Conflicts:
	docs/source/server/content_db.rst
	docs/source/server/crawling_depth_policy.rst
	docs/source/server/link_db.rst
	docs/source/server/task_server.rst
	docs/source/server/url_processor.rst
	docs/source/server/web_interface.rst