Potential breaking changes

• TypeScript users please read : Types have been almost entirely rewritten, which fixes a lot of issues with typing. But it may also throw errors that weren't catched before, especially if you don't annotate return types in reactive functions, see example. I'm very sorry for the potential breaking changes in a Release Candidate, but it's a necessary evil for the upcoming stable release.

New

• Reactive pollInterval (#613) closes #453
• Add global prefetch ApolloProvider option (#710)

Fixed

• Externalize apollo and graphql libraries (#722)