Deletes unused and outdated code, including and AST walker for Flux
queries and various Flux metaquery utilites.
Also moves the remaining modules in `src/flux` to somewhere under
`src/shared`. The `src/flux` directory was a vestige of a time when the
Flux related portions of Chronograf were contained to a single page, but
now these modules are used everywhere.
Christopher Henn
Brandon Farmer
Deniz Kusefoglu
Michael Desa
Mark Rushakoff
Andrew Watkins