API Key Validation

[Ferrisx4]

If the module attempts to use an invalid API key, the import will fail.

• If API key is rejected by NCBI, try to import anyway (NCBI doesn't require API keys, it just allows higher rate)
• Warnings to the user
• Validate API key at administration screen before saving

It would also be nice to be able to validate the API key before attempting an import (either by querying NCBI directly or checking for allowed patterns). Unfortunately NCBI's API key documentation doesn't seem to list what form their API keys will always adhere to.

[Ferrisx4]

Probably related to #218 to some degree.

At any rate, better validation of NCBI's response is needed (beyond erroneous API key issues).