Replace the stub implementation of invalidation with the proper
implementation. A ReadPathCache is added to each global so that it can
keep tracks of what target are associated to which read paths.
This commit changes the following method names across the codebase:
* `storeToDisk` -> `store`
* `loadFromDisk` -> `load`
This has been done since the storage is no longer bound to the local
storage.
Many Pipeline objects (Globals, Ranks, Kinds, Targets in a TargetList)
were ordered by load order, this makes the playback of traces difficult.
Moreover the order of loading of pipeline files also influences the
ordering of other elements (Step, Analys{is,esLists}). These are also
ordered to prevent incosistent ordering.
`DocumentError`s are the inteded way of propagating errors from the
pipeline to the frontend when a location is required to inform the user
of the error whereabouts.
Ivan Krysak