Initial version of v2 pull integration + project info v2

[MarcelGeo]

Resolved #280

• new pull mechanism using /delta endpoint, where pull changes between current version and server are calculated from delta items

• tests for both v2 and v1 features
• projectinfo v2 compatibility test

Fixes

• handle conflicting copy of versioned files properly without rebase logic

Pull logic updates

• in pull_project_async is check if server supports v2_pull

• If supports: get pull delta from server

• If not: calculate pull delta from files and projects config.json

• Then calculate delta items between local files and server (local delta) - delta needs to be applied to server

• Compare pull_delta and local_delta -> PullAction with actions needs to be done after files are downloaded from a server defined in PullActionType enum

• Starting download

• After download is finished -> call pull_project_finalize

• Method apply_pull_actions is then responsible to finalize PullAction based on type

[wonder-sk]

let's first do a bit of refactoring... the idea is that:

• we introduce a new class that captures project delta (added/updated/updated_diff/deleted) files
• the project delta class would be returned by get_pull_changes and get_push_changes
• there would a function that can combine server changes (from get_pull_changes) and local changes (from get_push_changes) and return a list of tasks to do at the end of the pull (e.g. copy, copy conflict, apply diff, delete - like PullTask in mobile app's merginapi)
• apply_pull_changes() would just go through the list of "pull tasks" and apply them, rather than again getting local changes and doing logic based on that