Refs #8922 Add support for nested history saving.
Refs #8922 Refactor history loading.
Refs #8922 Add support for loading nested histories.
Refs #8922 Fix bug with WorkspaceProperty.

Should only give the workspace a temp name if we have a pointer to a workspace.
Refs #8922 Add unit tests for nested WorkspaceHistory loading.
Refs #8922 Fix SaveNexus and SaveNexusProcessed to capture history.

SaveNexus and SaveNexusProcessed wouldn't append a record to the history.
This commit fixes that issue and leaves a record on the input workspace so the result is that we get a
complete history, but we lose the execution start time and duration.
Refs #8922 Fix unit tests.
Refs #8922 Remove commented out code in LoadNexusProcessed

It looks like history was loaded here at some point in the past. May as well remove this
while I'm here.
Merge branch 'feature/8922_history_loading_performance' into develop