Add integration tests for saild, and thus also sail :)

[novedevo]

this is a solid integration testing strategy IMO, as long as we believe saild should be a flagship implementation / example, i.e. it supports most valid usecases, or enough to reasonably cover sail

todo:

• more test cases
• testcase (re)generator - supply the client data and the generator records saild's responses to make a new testcase
• ignore text, only check response codes in integration tests