Add verification of apriori solutions before applying them

[stsci-hack]

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Another layer of protection against spurious or incorrect apriori solutions provided by the astrometry database would be to check that the new solution does not modify the CRVALs by more than some reasonable limit (< 10arcsec?).
This same check is being implemented for the astrometry database itself when it checks all solutions to be added to the database. However, the code should be aware of this potential problem and not assume that some other system will prevent it, since that has already resulted in problems with processing and the archive products.