Remove "Pivoter" code

[Brian Lewis]

This is very old, attempt to do some client-side pivoting. We have better established tools now, in particular XFilter to create crosstabs from Crossfilter, and also GridMaker at the SQL ( and REST) levels.

All this stuff can go.

[Brian Lewis]

API Controller PivoterController was not referenced in project anyway - removed

[Brian Lewis]

task(codebase): remove unused code for Pivoter on client

Resolves #1082

→ <<cset d2be9f01dc57>>