Fix schemaName in Apollo config

[pchmelar]

📝 Description

• This PR fixes schemaName issue in the Apollo config

💡 What’s new?

• As mentioned in Update Apollo to 1.0.0 and use via SPM Plugins #51, there was a problem with schemaName in the Apollo config file.
• Turns out that it can be resolved by adding "pruneGeneratedFiles": false to the config. 💪

😶 What’s missing?

• Nothing

📚 References

• Problem with schemaName apollographql/apollo-ios#2546

[pchmelar]

I've also included some additional minor improvements in this PR:

• Proper paths in SPM Packages
• Running Apollo from GraphQLProvider instead of RocketToolkit (reusability of .build in case where more toolkits are using Apollo)