upstreaming large refactor

[pca006132]

I did a large refactor (1a30d5b) to work on #208 and potentially solve other UI slowness issues. But there are two issues with this commit:

1. It is a large refactor. It changes the DAO significantly, and this affects a lot of the operations that require access to the DAO.
2. It will require some testing. The previous code hides DAO access in another thread, but blockingly wait for that in the UI thread. This avoids crashes enforced by Android on synchronous access tothe DAO on the main thread, but it is still blocking. It now perform synchronous updates on background threads and do not wait until it. I am not sure if I am doing this enough, and if this will cause data consistency issues (I assume not). So this probably requires more testing.

@eddyizm what do you think is the best way to upstream this?

[pca006132]

btw it is definitely not ready for upstreaming, just for the record

[eddyizm]

I think we should maybe make a list of things we want to test, create a test apk and get a few people to run the debug version.

I haven't looked over the commit yet but maybe we can implement parts of it slowly ish? guessing that will be hard but if any part of it could be sectioned off, that would make it easier to identify issues and we can include these chunks in the regular release as we have other folks help us test.

Just a thought, we should think about it more and I will spend more time looking over the code to get a better idea. I actually spent some time today to start implementing some automated tests, starting with unit tests. I think any real coverage would give us some semblance stability for these bigger refactors.

[pca006132]

Should be fine to chop it up. It will take some time to do so.

Re. automated test: Yeah that will be good. I don't have much knowledge about android dev, but I think there should be ways to mock a source provider instead of setting up a server for CI testing?