This commit prevents complete server failures caused by
`logger.CriticalIf` calls. Instead of calling `os.Exit(1)`
the function now executes a panic with a special value
indicating that a critical error happend. At the top HTTP
handler layer panics are recovered and if its a critical
error the client gets an InternalServerError status code.
Further this allows unit tests to cover critical-error code
paths.
Add compile time GOROOT path to the list of prefix
of file paths to be removed.
Add webhandler function names to the slice that
stores function names to terminate logging.
This is an effort to remove panic from the source.
Add a new call called CriticialIf, that calls LogIf and exits.
Replace panics with one of CriticalIf, FatalIf and a return of error.
