Refactor level IO

[lahm86]

An initial goal so we can use a single class per game version for reading and writing.

Stage 1

• [x] Rename BaseTRLevel to TRLevelBase
• [x] Create common level version enums and class
• [x] Create common base TRLevelControlBase class for IO

Stage 2

• [x] Rename TRLevel to TR1Level
• [x] Rename TRLevelNames to TR1LevelNames

Stage 3

• [x] Expand on common base TRLevelControlBase class to manage reading and writing
• [x] Merge TRLevelReader and TRLevelWriter into TR1LevelControl
• [x] Merge TR2LevelReader and TR2LevelWriter into TR2LevelControl
• [x] Merge TR3LevelReader and TR3LevelWriter into TR3LevelControl
• [x] Merge TR4LevelReader and TR4LevelWriter into TR4LevelControl
• [x] Merge TR5LevelReader and TR5LevelWriter into TR5LevelControl

Stage 4

• [ ] Create common classes for reading/writing and remove the various utility classes
• [ ] Move writing logic into TRXLevelControl classes