@log_call should have configurable level

[antonkulaga]

It is a huge headache that i cannot define log-level in he @log_call decorator

[mathrick]

+1 on that, no custom parameters are allowed, which makes @log_call about 10x less useful than it should be. Since Eliot's stance is that levels are just arbitrary values passed into the logging call, it should accept arbitrary values, just like regular .log()