Remove resultswriter/reader infra

[MichaelClerx]

DB stuff seems to be working now, so might be a good time to re-evaluate how we're reading/writing. Current structure was not so much designed as "lets see if this works"-ed.

Example of how it could be different:

• Have some sort of ActiveRow TestResult object that you create and modify, possibly with a commit() or sync() method that reads/writes to DB.
• Have a static class to fetch results, where each method has some query inside that does useful stuff and returns a list of result objects that match some hard-coded criteria

[MichaelClerx]

Ideas @martinjrobins @iamleeg @fcooper8472 ?

[iamleeg]

What's currently there isn't far from ActiveRow:

• combine reader and writer into a single class. Pass the primary key (the row ID) in the __init__(): if it's non-None, then use it, otherwise create a row and use that
• there already is a write() method but it does nothing because every write currently commits its changes. This can be changed so that writes are explicit.

[MichaelClerx]

A scenario for writing would be:

1. Create a test result, enter basic data (outcome=running), send to DB
2. Finish running test, update DB with outcome of test

Scenarios for reading:

• Get all completed runs of test X, that have a KLD value, group (and sort) by (pfunk_commit, pints_commit) and return a nested list
• Like before, but with some selection based on times
• That kind of thing!

[MichaelClerx]

pints-team/change-point-testing#25