expose EE version in lua

[czenker]

This is how it could look like to prevent a scenario from loading in a too old version of EE. It is better than showing an arbitrary "this function does not exist" error somewhere during a running scenario.

local requiredVersion = 20200409
if getEEVersion == nil then
    error(string.format("This scenario requires EmptyEpsilon %d or higher", requiredVersion))
else
    local version = getEEVersion()
    if version ~= 0 and version < requiredVersion then
        error(string.format("This scenario requires EmptyEpsilon %d or higher, but you got %d.", requiredVersion, version))
    end
end