Added Microbe saving/loading in editor.
Uses existing serialization to read/write foo.microbe files in creations/microbe.
Uses new version file to record save versions, in case of backwards-compatibility issues.
Merge pull request #168 from Revolutionary-Games/131-savable-creatures

Added Microbe saving/loading in editor.
Uses existing serialization to read/write foo.microbe files in creations/microbe.
Uses new version file to record save versions, in case of backwards-compatibility issues.
Merge branch 'master' of https://github.com/Revolutionary-Games/Thrive into 165-rolling-grid