Pagination initial support

For now, just the memory storage implementation: next to come
Ordering initial support

For now, just the memory storage implementation and just for state: next to come
Simple implementation of filtering in in-memory adapter and in web console
TODOs update
ensure correct state transitions in execution plan
speedup tests
add sequel adapter
ensure out/input is settable only in correct phases
remove forgotten resume method
store meta data in step
add meta data to ExecutionPlan
TODOs update
Do not store Steps inside ExecutionPlan

* fix serialization to hash for objects deeper in hash
* remove ExecutionPlan#new_plan_step method, unified with #add_step
* disable other than Sequel adapters for now
* speedup test by making them share one instance of World
support filtering, pagination and ordering in Sequel adapter
store errors in steps instead of actions
fix meta data storing in Sequel Adapter and filtering
TODOs update, removing old persistence adapters
move SequentialManager under Parallel executor
Merge pull request #30 from pitr-ch/refactor

Sequel adapter, querying