feat: route installer

[AMFTech512]

This package enables packages to install their routes into other packages. It has a function and an action that can be invoked during the installation of a package. A common use case for this is if a package has a special admin interface to configure it. It can add itself to the creator's site. To use the function, call it with the following payload:

{
    "runtimeData": {
        "packagePath": "PATH OF PACKAGE WITH ROUTES TO INSTALL"
    }
}

Problems left to solve:

• Somehow we need to determine what the package version id is for the package we're installing into. See https://github.com/trufflehq/truffle-packages/pull/71/files#diff-fd307a40fbacae320f112c47e318ad588fa318e1ac495bdccfcf156accd1b231R50
• If the parent package is redeployed (often will be the creator's site), the routes installed by this package won't be in the new version, so someone/something will have to rerun this function every time a creator redeploys their site.

[rileymiller]

I think we should be able to add some sort of flow to truffle-cli where it compares all of the routes on the previous package version to the fs routes and should prompt the user on whether they want to explicitly delete a route, and if so, the route doesn't get ported over. Imagine we'd also be able to add a flag to truffle-cli deploy that specifies some sort of default behavior so that process can be run headless in CI.