sfeed_opml_import: import from OPML

OPML is a XML-based format used for importing or exporting a list of feeds.
Some programs that support it are newsboat, rss2email, Mozilla Thunderbird.

The program sfeed_opml_import reads feeds from an OPML file and writes a
sfeedrc configuration file (used by sfeed_update):

Import from newsboat:

	newsboat -e | sfeed_opml_import > ~/.sfeed/sfeedrc

Import from rss2email (v3):

	r2e opmlexport | sfeed_opml_import > ~/.sfeed/sfeedrc
