IndexedDB: Joined histograms in one OS with key suffix.
FeatureChunkCache: minor renaming.
Created alignment-renderer and variant-renderer.

As start point, aligment-renderer is a copy of bam-renderer.
alignment-renderer: first draw.

Adapter faked.
Merge branch 'feature/alignment-and-variation' of github.com:jmmut/jsorolla into feature/alignment-and-variation