Tag next-stable branch instead of default before next release.

Will more accurately reflect upcoming release.
Do not explicitly specify database in config file.

Bug preventing this fixed here https://bitbucket.org/galaxy/galaxy-central/commits/fe0cdf1166a841eb4b06dae4b40f552d12d947c7 and is in next-stable.
Disable explicitly setting debug in galaxy.ini.

I think I figured out why you thought it still needed to be set - the change was sitting in next-stable for a while before being merged back downstream into default by Nate a day later (this was my own fault - I should have merged it right away). During that time I believe this Dockerfile was targetting default instead of next-stable.
Merge pull request #7 from jmchilton/october14_config_fixes

More configuration tweaks.