AP_Scripting: add binding and helper to get old params

[IamPete1]

Adds the ability to get params by token rather than name. This paves the way for moving functionality out of c++ and into lua by enabling param conversion.

For example to get the value of FORMAT_VERSION

old_param = Parameter()
assert(old_param:init_by_info(0, 0, 2), 'could not find param')
gcs:send_text(0, string.format("old param = %f", old_param:get()))