v0.21.0

• o2-alf: added option --dim-log-file to define a local file to log DIM RPC calls. e.g. o2-alf --dim-log-file=/tmp/alf.log,1000000,4 would create in /tmp a set of 4 rotated 1MB files (alf.log, alf.log.1, alf.log.2, alf.log.3)