telnet connections fail if reply is larger than 32000

[domschl]

Some parts of the API do not support telnet's blocking=False parameter, and blocking=True cut s all replies to 32000 max. Operation that rely on larger requests (wildcards) fail.

Fix:
allow usage of blocking=False in APIs (e.g. get_readings())
increase default from 32000 for blocking.

deprecate telnet.

[domschl]

Fixed in 0.6.2, telnet by default uses non-blocking. Blocking operation can be forced with parameter blocking=True for all get*() operations.