Set NODE_REPLACE_BY_FEE to let peers find us
Preferentially peer with replace-by-fee nodes

Tries to maintain 8 outgoing connections and reserves 3/4 of the
incoming connections for replace-by-fee nodes.
Log delta bytes
Fix economics of replacements

Previously bandwidth of prior transactions wasn't always being paid for.
Allow children to be replaced

If a conflicting tx has children they can now be replaced as well.
Fix merge
Merge branch 'replace-by-fee-v0.9.3rc2' into replace-by-fee-new

Merge Petter Tood's replace-by-fee patch with the bitcoin 0.9.3 version together to the new branch