AlignmentRenderer refactor. Next, multisample render.
Developed multisample alignment render.
Merge branch 'feature/opencga-0.3' of https://github.com/opencb/jsorolla into feature/several-alignments
modified track interface to allow different dom structures
updated height and autoheight calculations
Improved multisample render support. Work in progress.

It's necessary to add a sid in the opencga-adapter to test.
Improved multisample drawing.
Updated MemoryStore to share IndexedDBStore interface.

It is needed an extra parameter "category", which should be a string.
This provides another level of classification.
About to update VcfMultisampleRenderer. WIP.
Developed on multisample divs. WIP.
Fixed bugs.

Bugs were related to displayed area and svg height.
Added scroll per sample and logarithmic coverage.
IndexedDB: added getObjectStoreNames.
Merge branch 'feature/opencga-0.3' into feature/multialignments
Improved alignment histogram rendering.

by the moment, without autoheight.
Minor fixes to histogramRenderer.
Merge branch 'feature/variantRenderer' into feature/multialignments
First draw of variant renderer.

The render can handle several samples. Next is several files, each one
in its own div.
Fixed some issues related to FeatureChunkCache.
Improved variant rendering with proper data.