Fix table logging to respect hierachy

Currently the logging for the CassandraTable class blithely takes the
name of the table as the name for the logger. This is undesirable for a
number of reasons most salient being:

- We are potentially trampling on other peoples namespace and logging
  hierachy
- We make it impossible to silence all logging on tables to a custom log
  level without adding an explicit directive for each table name

This commit fixes both these issues by simply taking the class name.