Replacement methods created for [Level]Exception

In Logger class
* New public method added Log(LogLevel, String, Exception)
* Method overloads added to replace eventually any
[Level]Exception(String, Exception) named methods
Default value added in EnviromentLayoutRender

Default value can now specified on EnviromentLayoutRenderer along
variable name. When the variable has not defined the layout will return
the default value instead.
Revert "Revert"

This reverts commit 0f46d43425a4ed967a627c839b784bc4f9bd8d65.
Merge pull request #344 from ie-zero/master

Replacement for [LogLevel]Exception methods