Allow specifying a list of columns to log

[erik-kallen]

I suggest introducing a property Columns which can be used to specify what to log to Azure. Eg.

<param name="Columns" value="Level,Message,EventTimeStamp,ThreadName,MyProperty" />

If you like the feature, I can probably do it myself and create a PR.

[GrzegorzBlok]

It is possible to use PatternLayout to customize logged data. See if it fits you.

<appender name="AzureTableAppender" type="log4net.Appender.AzureTableAppender, log4net.Appender.Azure">
      <param name="TableName" value="AzureLog" />
      ...
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="[%property{methodAndUri}] %method -- %message %exception" />
      </layout>
</appender>

[erik-kallen]

But I want to log the properties in separate columns, just like it is. It is just that I want to not have all of them.