The work on book download error logging highlighted  some changes in how we can use logging to crashlytics more efficiently. We should reflect this by updating the terminology in NYPLErrorLogger and reorganizing some of the log functions.

Change:

• remove some of the custom log methods that are used only once in favor of the more generic "logError" methods
• fix logging of Severity: currently most log functions log stuff as "errors" even when they are warnings. But: do we even need this severity distinction? it's only searchable via BigTable.
• reorg list of functions semantically
• "context" to summary / title
• use error codes to group similar cause of errors together (e.g. a "bookDownloadFail" code for all download error logs) and context/summary to have a specific error message