- 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.

This reverts commit 13f3481e.

Conflicts:

	doc/zmq_device.txt
	doc/zmq_tcp.txt

- fixed unwrapped text in new man pages
- fixed over-long lines in older pages, where possible
- removed reference to old standalong devices from index page
- added refernce to new zmq_device[3] documented from index page
- some minor spelling corrections

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