Carrying - Handle simultaneously carry action

[Kexanone]

When merged this pull request will:

• Use replicated variables on character controller for determining whether someone is carrier or carried
• Fix Carrying - Breaks when two players try to initiate carrying simultaneously #98

Background:

• The previous approach determined whether someone is carrier or carried based on whether the helper compartment is part of the entity's hierarchy. However, this approach leads to race conditions, since it takes several frames for the carried player to move into the helper compartment and become a child of it.