Expose method to customize the MetroLog.LogManager.DateTimeFormat

[ptedeschi]

The DateTimeFormat is defined as an internal const. Developers should be able to change the format string.

[Aymeeeric]

I agree with this suggestion ... I will also add customization to the timezone that seems impossible.

[eresing]

I also would like to change the time from UTC.

[Raamakrishnan]

I used this workaround to show local time using a custom layout. http://stackoverflow.com/questions/43992460/logging-in-local-time-in-metrolog/43993585#43993585 We can use the default layouts as templates https://github.com/onovotny/MetroLog/blob/dev/MetroLog.Shared/Layouts/SingleLineLayout.cs https://github.com/onovotny/MetroLog/blob/dev/MetroLog.Shared/Layouts/FileSnapshotLayout.cs