- handle socket errors directly and re-throw other exceptions
- update exception error logging
# maybe we should also trying to re-start the connection
- move parsing data into try/except block and remove return
# this should always log the cycle time, event in case of exceptions
- move entity logging into read function
# avoid double output of all obis values currently in the response - only the last value will
# be used
- update documentation header
- remove cycle update and instead of them try continuous reading from device
  and update items directly
- make SML plugin registerable multiple times by changing class variables
  to instance variables
Revert "- remove cycle update and instead of them try continuous reading from device"

This reverts commit 20c366b5cfbbab647d22d61be0ce8456d4b95939.

Conflicts:
	plugins/sml/__init__.py
- reconnect on reading errors instead of still trying to read from socket
- change _refresh() to retry reading data on connection errors five time before
  giving up
# will then try to read data in the next cycle
Merge pull request #126 from ohinckel/issue-112-sml-read-deadlock

Fixes issue 122: SML read deadlock