Upgrade the erlang-server dependency from cowboy1.x to cowboy2.x

[feihongmeilian]

Now we are upgrading the erlang-server code generated by openapi-generator from the dependency on cowboy1.x to cowboy2.x.

Simple case has been verified, but I look forward to more in line with the way cowboy.rest advocates, so I need some time to understand the mode of cowboy.rest . Of course,I also need to completed the ticket from my company.

So it is estimated that the first PR will be 2018.11.10.

BR/feihongmeilian

[wing328]

@feihongmeilian thank you. Look forward to your contributions.

[wing328]

Closed via #1364