Handling of 'GROUP BY' and selected columns

1. Ensure correct queries if the rest_of_query contains a 'GROUP BY'.
2. Create a correct subquery if there's only one id column.
Partially fixes #437
SELECT DISTINCT clause with ORDER BY for MSSQL

SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause.

Partially fixes #437
[mysql] support "disabling" abandoned connection cleanup thread

due leaks on hot re-deploys - will probably be shutdown by default on the next major version or AR-JDBC
re-build jar using JRuby 1.6.8 on Java 6
Fix rails 4-0-stable compatibility
go for 1.3.6
add emulate booleans option for derby adapter
add tests for derby emulate booleans option
Merge pull request #533 from mark100net/derby-emulate-booleans-option

add emulate booleans option for derby adapter
jdbc-hsqldb 2.3.2
jdbc-postgres 9.3-1101
Merge branch 'master' of github.com:jruby/activerecord-jdbc-adapter

* 'master' of github.com:jruby/activerecord-jdbc-adapter:
  add tests for derby emulate booleans option
  add emulate booleans option for derby adapter
FireBird's DB meta-identifier is 31 chars maximum, thanks @mariuz (#538)
fix db2 remove_column for ActiveRecord 4
updated jaybird to 2.2.4
Fix connection without user and password
appraise / update to latest of AR
remove_column compatibility with Rails 4.x for Oracle, Derby and MSSQL
[mysql] needs to `reconnect!` when recreating database (fixes 539)

aligning with https://github.com/rails/rails/commit/2088bf27981137a2c6c8b2f718f33b417b4045af
try resolving config 'database' (if missing) from JDBC url: in rake tasks