[mssql] needs a connection_alive_sql specified 
since jTDS does not support JDBC 4.0 isValid :
```
  Java::JavaLang::AbstractMethodError: 
net.sourceforge.jtds.jdbc.JtdsConnection.isValid(JtdsConnection.java:2812)
arjdbc.jdbc.RubyJdbcConnection.isConnectionValid(RubyJdbcConnection.java:2141)
...
```
unify rake tasks 'registration' - so we do not have to do it twice 
(for 2.3/3.x and 4.0 separately)
refactore expect_rake_output to stub $stdout instead of relying on mocha
share db:test:purge implementation among tasks for AR 3.x/4.x
create db for embed databases - derby's drop does not handle purge well
[mssql] collation and database_exists? helpers for SQLServer
avoid {}.deep_dup + updated MS-SQL rake tests
Fix SQL server version matching on SQL Azure
Fix README instructions for connecting to Azure SQL Database
[DB2] should set schema on configure_connection
- make sure schema is 'resolved' once (even if nil)
-  introduce schema / schema= methods
- due removed lob_callback_added? add a handle_lobs? (dummy) method
- improve structure_dump a bit (close Java result sets)
fix a typo in method name
re-use column/table quoting that's already available on structure_dump
[DB2] database tasks - with a tested (and fixed) structure_dump