- Clarify ZMQ_LINGER, zmq_close (), zmq_term () relationship
- New socket options
- Clarify thread safety of sockets and migration between threads
- Other minor and spelling fixes
Signed-off-by: Martin Lucina <mato@kotelna.sk>

This reverts commit 77a3c36f.

* Added documentation for zmq_deviced, which we're developing
* Created consistent page footer in documentation template
* Page footer notes doc authors and copyright statement