new slick execution context for async db calls
define execution context outside the trait
added optional typed ids
changed ProductionSite to type safe id
changed Site to type safe id
renamed untyped ids to prepare for renaming typed ids to id
Made SlickDDLPlugin much simpler and more robust.

Warning: This is a source incompatible change.

Improvements:
* more flexible and robust because it communicates with the user app via the play.api.db.slick.AutoDDL singleton object instead of automagical table object discovery
* safer: scalac checks imports and objects referenced in play.api.db.slick.AutoDDL (unlike the existence of a package mentioned in config like it was before)
* less reflection: now only happens in def fetchAutoDDLobject and just a bit
* does not override user written evolution scripts, but shows error message instead
Merge branch 'master' into scaladays2013

Conflicts:
	samples/computer-database/app/controllers/Application.scala
	samples/computer-database/conf/application.conf
Merge branch 'topic/autoddl' into scaladays2013

Conflicts:
	samples/computer-database/conf/application.conf
Fixes discouraged static table object and SlickDDLPlugin when referring to vals in AutoDDL

* Replace static singleton table objects with vale. From the Slick docs "Also make sure that an actual object for a table is not defined in a static location (i.e. at the top level or nested only inside other objects) because this can cause problems in certain situations due to an overeager optimization performed by scalac. Using a val for your table (with an anonymous structural type or a separate class definition) is fine everywhere." http://slick.typesafe.com/doc/1.0.1/lifted-embedding.html#tables
* SlickDDLPlugin now handles LinkageError, which can happen, when referring to vals in AutoDDL, because it is loaded via reflection.
Merge branch 'topic/autoddl' into scaladays2013

Conflicts:
	samples/computer-database/app/models/Models.scala
	samples/computer-database/app/models/package.scala
fixes tests and bug related to package object models, custom AutoDDL object for SlickDDLPlugin

* the static location of the AutoDDL plugin object can now be configured
* moves table object vals out of package object models to avoid https://github.com/playframework/Play20/issues/867
* fixes SlickDDLPlugin tests
Merge branch 'topic/autoddl' into scaladays2013

Conflicts:
	samples/computer-database/app/Global.scala
	samples/computer-database/app/controllers/Application.scala
	samples/computer-database/app/models/Models.scala
	samples/computer-database/app/models/package.scala
fixes NameGenerator, enables new SlickDDLPlugin