[Feature] Unique entity names

[brenocq]

Feature description
When creating a cmp::Entity, the user currently needs to hardcode the EntityId. While this works, it would be better to identify entities by their names instead of IDs. Names for the entities should be unique. This will not only improve code readability, but also ROS topics as shown in #60. @ahzary also noted that names should not contain special characters

Tasks

• Make sure names are unique
  • When conflict is detected, something like (1) should be added at the end
• Make sure names only have allowed characters
• Encode entity name as StringId
• Map entity name's StringId into EntityId
• Update entity window to not show name component
• Allow editing the entity name by double-clicking the name in the scene tree