Extend SKD with new methods of Files API

[Hustred]

New calls added recently to FAPI2:
GET /files-api/v2/projects/{projectId}/file-types
POST /files-api/v2/projects/{projectId}/locales/{localeId}/file/get-translations

We should provide support for them in SDK

[dimitrystd]

One more similar request #5

[jhansche]

This also seems to be missing the "Download translated files as a zip" API:

https://help.smartling.com/v1.0/reference#get_projects-projectid-files-zip
GET /files-api/v2/projects/{projectId}/files/zip?localeIds[]=&fileUris[]=

Given that this issue is almost 2 years old, should I just create a new issue for it? Or implement it myself and make a PR?

[dimitrystd]

We will be happy to accept your PR.

[jhansche]

PR opened: #45