Initial commit of Zend\Db\Sql\Ddl architecture
Added constraints
Added Mysql CreateTable specific handler
Removed various empty classes
Added test stubs
Updated CreateTableTest
Zend\Db\Sql\Ddl
More tests and docblocks
Merge pull request #4311 from ralphschindler/feature/db-ddl

DDL support for Zend\Db
[#4311] CS review

- Made sure file-level docblocks were consistent throughout
- Alphabetized constant and property declarations
- Ensured methods were in public -> protected -> private order
- s/$self/this/ in all @return annotations
- Ensured annotations were available and correct for all public methods
- A few minor formatting changes for readability
Merge branch 'feature/4311' into develop

Close #4311