mkcollector: make code compliant with the v2.0.0 spec

[bassosimone]

I am about to publish the new collector spec. Code should be updated to use it.

[bassosimone]

I have took a pass at reading the specification and flagged what we need to do in order to have our code compliant with the v2.0.x specification of the collector. Issues:

• mkcollector: add socks5 client support #15

• mkcollector: implement the single measurement submission flow #16

• mkcollector: input_hashes not needed for opening #17

• mkcollector: test_start_time not needed for opening #18

• mkcollector: check supported_formats during open #19

• mkcollector: validate measurement on submission? #20

• mkcollector: validate measurement on submission? #20

Since the number of issues above is starting to be not so small, I am creating a milestone for addressing all these issues, to avoid spamming the top-level kanban.

[bassosimone]

So, since I've created a milestone that groups all the related issues, this issue can go. Bye bye.