Find possible type errors in jobdefinitions on jobserver start (migrated)

[michaelschnyder]

originally posted by @michaelschnyder on Mar 22, 2015 on the old repo

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When a job has an incorrect Type for the class, this gets an error while executing the job since the CLR-Type of the JobClass cannot be found. (Already implemented, Fails at the end)

Proposed change:
Give the JobbrServer the possibility to check (maybe with the help of the runner) all defined jobs and warn for not existing type-names.