Remove CENT-output free transaction rule

Remove the rule that all outputs of free transactions must be
greater than 0.01 XBT. Dust spam is now taken care of by making
dusty outputs non-standard.
Lower maximum size for free transaction creation

Changes the maximum size of a free transaction that will be created
from 10,000 bytes to 1,000 bytes.

The idea behind this change is to make the free transaction area
available to a greater number of people; with the default 27K-per-block,
just three very-large very-high-priority transactions could fill the space.