Correct typo on documentation

The constant was written JDTS instead of JTDS.
Since people copy and paste, it can be a tricky one...
Fixing substring issue that prevents detecting a query that contains *
[mssql] add a has_many :though tests + re-arrange tests a bit (closes #171)

NOTE: a failure commit fd27edfe08867235 fixes was only reproducable with 3.0 and 3.1 while running in JRuby --1.8 mode