Use conventions to support GraphQL mutations and adjust query names

[mattjohnsonpint]

Implements naming conventions for functions that alter how they are represented in the generated GraphQL API:

var queryTrimPrefixes = []string{"get", "list"}
var mutationPrefixes = []string{
	"mutate",
	"post", "patch", "put", "delete",
	"add", "update", "insert", "upsert",
	"create", "edit", "save", "remove", "alter", "modify",
}

• If a function name starts with a mutation prefix, then it's a mutation, not a query.
• If a function name starts with a query trim prefix, then it's a query and the prefix will be trimmed away.
• Otherwise, it's a query.

For example, consider functions named getCustomers, searchInventory, and updateProduct`. They now will get GraphQL schema of:

type Query {
    customers(...)
    searchInventory(...)
}

type Mutation {
    updateProduct(...)
}