special encoding limits redefined, and all the config options for special encodings added in the example redis.conf file

Original report and fix:
http://code.google.com/p/redis/issues/detail?id=404

SUBSTR is renamed to GETRANGE to have better consistency between command
names (with SETRANGE as its dual). GETRANGE is still aliased as SUBSTR.

previouse INCR implementation restored, was actually faster for some reson not fully clear at the moment

HGET HMGET are now COW friendly, plus API refactoring and changes needed for the new implementation.

Move logic concerned with setting a bit in an sds to the SETBIT command
instead of keeping it in sds.c. The function to grow an sds can and will
be reused for a command to set a range within a string value.