Avoid logging BLOB values

[etedpet]

BLOBs are probably not that interesting to log. Also they take up a lot of space when printing in ASCII-format. Logging just a few large blobs (can be of MB size) will fill up the logs.

Example log output from a prepared statement (with small blobs):
1570025092487|127.0.0.1:45176|127.0.0.1|cassandra|ATTEMPT|UPDATE "standard1" SET "C0" = ?,"C1" = ?,"C2" = ? WHERE KEY=12345 [0x28029cc8622a9724bf1cf40452459cffcf8d59c9ab5ebb00c91ff72de420d1a346b9, 0x6b986a3cb238eafd3953c7109ca2b92c7ece025076ffa573623b7994a915fb9ea209, 0x11c6d2fb29c9f643dae00c72e9f79a9f0858fd93bf1bbd79cd24d4124971a99ba9e8]

It should be possible to configure whether or not to print the blob values when logging prepared statements. The actual blob could be replaced by a "marker" (e.g. <BLOB>) to indicate that a blob was present. For example:
1570025092487|127.0.0.1:45176|127.0.0.1|cassandra|ATTEMPT|UPDATE "standard1" SET "C0" = ?,"C1" = ?,"C2" = ? WHERE KEY=12345 [<BLOB>, <BLOB>, <BLOB>]

This issue is related/similar to #124. Maybe both of them are relevant?

Note that CollectionTypes (LIST, SET, MAP) can also contain blobs. These values should also be considered (not logged) if "normal" blobs are configured not to be logged.