Adding serialization support.

Initial pass at adding serialization support.
Added ability to reset session.

Fixed issues with NULL active source as well.
Cleaned up reset mechanism.

This fixes the issue where we ended up with two layouts when the state
was loaded.
Render view when ViewPropertiesPanel is updated.
Added ability to serialize/deserialize several modules.

This now wraps up the serialization logic to serialize modules with
minor API cleanups.
Added ability to save active items.
Added ParaView version to the state file.
WIP: refactoring recent files.
Merge pull request #8 from cryos/fixup_recent_files

Fixup recent files