Import/export/package cleanup

[rosskevin]

Goal: Address inconsistencies with import/exports, some type naming, and package creation

Summary: Ultimately, we were building and maintaining a browser.ts and server.ts and the payoff was negligible. Simplify indexes/builds/imports/exports and related names for consistency.

• use index.ts as primary accumulation of exports
• update exported types to be more unique to avoid collisions (pattern is set by Query.tsx more work needed here as we refactor graphql.tsx into Query/Mutate/Subscribe)
• update deprecated rollup configs
• measure only react-apollo.umd.js bundle (so small this is not worth maintaining/compiling two packages)
• reduce bundlesize limit to help show errors
• adjust prepare-package.sh to point to correct files
• revert tsconfig (mine) change to unsure es2015 is produced for optional package.module use
• move umd output in package to umd dir