WIP incorporate prototype PCA
Rough, but working PCA

- With selectable dimensions!
Fix dimension selection
Fix PCA calculation
Convert to RMS distances
Include computing the distance matrix (not used)
Merge branch 'master' into pca

Conflicts:
	app/js/compare.coffee
Merge branch 'master' into pca
Improve PCA option handling
Improve layout of axes on MDS plot
Disable the heat map when looking at the MDS plot
Remove dead code from PCA
Add method to set slider & text value
Add bar chart of MDS dimension magnitude to MDS plot
Update changelog
Tweak help for build-embed.sh
Add some basic docs for the MDS plot