Refactor: improve debug logging (log catched exceptions)

[kares]

tried to normalize traces involving :filename or :path to be more consistent - easier to grep.
otherwise the intent is mostly (debug) logging exceptions the plugin's expected to rescue and continue running.

particularly, I wasn't sure why a watched file keeps going through the read loop (having new content)
but comes out as never reading anything on Windows (e.g. from here), knowing whether there's an EOF or file-access gone wrong would confirm whether there's a deeper issue in the plugin or not.

have also raised a few traces to the debug level - ones that seem to provide more value than just tracing what the plugin is processing atm.

[andsel]

Generally LGTM, but there are some tracelog not guarded by logger.trace? &&. If we apply the rule to lazy evaluate the log expressions, probably it should be applied everywhere a tracelog is used, WDYT?

[kares]

added logger.trace? && ... guards + a few on debug as well (hot paths) but generally that wasn't much of the intent here.

[andsel]

Thanks @kares LGTM