POM-9. Upgrade to Avro 1.7.5

issue: https://jira.kiji.org/browse/POM-9
review: https://review.kiji.org/r/1013
SCHEMA-540. Avro 1.7.5 accepts any Object where a string is required

- Updated TestFinalColumns to not test against string/int.
- Fixed TestReaderSchema error messages.

issue: https://jira.kiji.org/browse/SCHEMA-540
review: https://review.kiji.org/r/1020
KijiSchema API for level 1 security
Set permissions on table creation; make KijiSecurityManager a property of a Kiji instance
IllegalArgument -> IllegalArgumentException in DeleteTool
interface + impl
small fixes