#48: Atomic files

[gwendalF]

Use atomic files whenever we want to use files. It ensure there are written atomicaly. Also we have the possibility to manage the case when the file is already present and do something with the data. Currently it's just overwritten but something better can be done
Fix #48

[kirillt]

@gwendalF have you implemented this, too?

If several versions with same number are found, take the version with local device id and log warning about conflicted versions. These conflicts can come only from remote devices, locally we can't produce conflicts.

[mberry]

Adding a Clippy CI check is good, but I'm getting 1 error here:

arklib/src/index.rs

Line 78 in 4dc4709

let file = File::open(&index_path)?;

It wants the borrow removed

[gwendalF]

Adding a Clippy CI check is good, but I'm getting 1 error here:

arklib/src/index.rs

Line 78 in 4dc4709

let file = File::open(&index_path)?;

It wants the borrow removed

We can remove the borrow since it does not appears to be used somewhere else so we can move the path on the open function

[gwendalF]

I've updated the case to not override properties. May need check because there is a bunch of clone and staff, so we can surely do it better.

May need a visitor pattern to merge two serde_json::Value

[gwendalF]

@kirillt I've updated the Link to use your solution of tempfile and moving to destination

[kirillt]

Good job