Merge pull request #49 from NamelessCoder/exceptiontemplates

[TASK] Further improve built-in FE exception template and BE handling
[TASK] Tolerate and report errors in BackendLayout

This makes fluidpages exit silently and use NOTICE debug messages in the backend layout processor class when no template is selected, when configuration cannot be detected, when template contains errors and when template does not contain a grid.
[TASK] Special WARNING debug message if native view not configured
[TASK] Custom WARNING debug messages on path / file problems