Update community information:
The Spanish mailing list are down.
The Polish web URL was wrong.
Update webresources information.
In the community.xsl, the LinkedIn group id was wrong and the
last activity in the twitter @freebsdblogs account was in 2013.

Patch by: carlavilla@
Reviewed by: bcr@(mentor)
Differential Revision: https://reviews.freebsd.org/D23041