Implementing delayed weight application per the SONATA spec (From PR#58))

[darshanmandge]

Overrides are applied immediately after connection creation. However, the SONATA spec's delay field specifies when weight changes take effect during simulation (e.g., apply the weight change at t=500ms).

We should support delayed weight application per the spec. Add it to TODO and implement in future PR, or try to add to it here.

Originally posted by @darshanmandge in #58 (comment)