core (logs): added formatting, name filter and outputs management: - formatting is inspired from, and use when possible, standard logging. "message", "levelname", and "name" are the only format managed, depending on backend more can be managed (standard backend formats are specified in official python logging doc) - name filter use regular expressions. It's possible to log only plugins with SAT_LOG_LOGGER="^sat.plugins". To log only XEPs 96 & 65, we can use SAT_LOG_LOGGER='(xep_0095|xep_0065)' - output management use a particular syntax: - output handler are name with "//", so far there are "//default" (most of time stderr), "//memory" and "//file" - options can be specified in parenthesis, e.g. "//memory(50)" mean a 50 lines memory buffer (50 is the current default, so that's equivalent to "//memory") - several handlers can be specified: "//file(/tmp/sat.log)//default" will use the default logging + a the /tmp/sat.log file - if there is only one handler, it use the file handler: "/tmp/sat.log" is the same as "//file(/tmp/sat.log)" - not finished, need more work for twisted and basic backends