Better modularization of async container's context

[JoaaoVerona]

Right now, when AsyncContainers are created, they receive an unique, fresh context, which have as it's parent the context where the async is being created.
For example, the script...

i = 0
j = 5

async {
  i = 1000
}

sleep(50)
println(i)

... will print 1000, because the async container have full access to the main context, thus changes to variables will also be reflected in any other component which also access the main context.

A proposal for modularization of async container's context is defined as:

• continue giving them an unique, new context
• creating a copy of the current parent context, and attributing it as the new context's parent

This way, the async container can access any variables on the parent context, but their values will be calculated once (it is: at the time the async container starts). Therefore, any changes made by the async container will NOT be reflected outside it, since the parent context was COPIED and not directly referenced.

[JoaaoVerona]

This issue will NOT be implemented until #8 is fixed.