Misc functions

[Lorak-mmk]

This is the issue for all functions that that fit anywhere else.

List:

• [ ] cass_consistency_string
• [ ] cass_write_type_string
• [x] cass_error_desc
• [x] cass_log_cleanup
• [x] cass_log_set_level
• [x] cass_log_set_callback
• [x] cass_log_get_callback_and_data
• [x] cass_log_set_queue_size
• [x] cass_log_level_string
• [ ] cass_alloc_set_functions

First 3 and cass_log_level_string should be really easy. I don't think the rest can be implemented in any meaningful way without a lot of work - we should probably skip them for now.

[Gor027]

Support for logging will be added in this PR.

[roydahan]

The missing ones are part of the document plan, will have their own issue.