[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
[TASK] Report configured instead of resolved path when path does not exist
Merge pull request #51 from NamelessCoder/errortolerance

[TASK] Improve error tolerance and provide better debug messages