[#863] Add timestamp to morley-client logs

Description

Problem: Timestamps are very useful in logs, but morley-client logs do not have any.

Solution: Add timestamps to co-log output.

Problem: Morley-client logs, together with timestamps, severity level and source location get pretty unwieldy. Additionally, source locations are usually not very informative, so those could be in most cases omitted.

Solution: Only display source location in high-verbosity mode, i.e. if it's higher than 2 (which is more verbose than "debug").

Related issue(s)

Resolves #863 (closed)

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