Option to change format from [loglvl] [timestamp] to [timestamp] [loglvl]

[shayanhabibi]

options.nim

  chronicles_lvl_first {.strdefine.} = "on"

  ##

  const logLevelFirst* = handleYesNoOption chronicles_lvl_first

log_output.nim

  when logLevelFirst: appendLogLevelMarker(r, lvl, true)

  when r.timestamps != NoTimestamps:
    when logLevelFirst: append(r.output, " ")
    writeTs(r)

  when not logLevelFirst:
    when r.timestamps != NoTimeStamps: append(r.output, " ")
    appendLogLevelMarker(r, lvl, true)

Human consumption of the output might make sense to have the log lvl prior to the message since time stamps are less relevant on human message consumption than the log lvl and message yet adds a large space between the two.