Turn off test
Add available identifiers to plan descriptions, instead of tracking introduced identifiers
Throwing the wrong exception.

We were not throwing and catching the same exception, this lead to exceptions
leaking out to end user when using node index seek with a non-existing id.
Merge pull request #3358 from systay/plandescription-details

Add available identifiers to plan descriptions
Merge pull request #3371 from pontusmelke/throwing-wrong-exception

Throwing the wrong exception.
Cleaned up ExecutionContext
Produce RowSpec when creating Pipes
Turned ExecutionContext into a trait

MapExecutionContext is the main implementation of ExecutionContext
WIP