Simplify implementation of command buffer

[friflo]

Current implementation details:

• Its uses an internal Dictionary which impact performance on Playback()
• Added commands are not executed in insertion order
• One or zero structure change is applied for each entity

Change:

• Simplify implementation by removing Dictionary
• Ensure insertion order of added commands
• One or zero structure change is applied for each entity.
  Restriction: commands to a specific entity need to be added sequentially.