Specify module name and package versions when create app from model file

[yxuco]

When creating app from a model file, I want to provide a go.mod file that specifies the app's module name and versions of some required packages, and so the generated source code will use the provided file as the base go.mod. For example, flogo create command can accept the following input file, and so the generated source code will use the specified module name and forked package repo version for flogo core and flow.

module github.com/myorg/myproj/myapp
go 1.14
replace github.com/project-flogo/core => github.com/myfork/core v1.2.1
replace github.com/project-flogo/flow => github.com/myfork/flow v1.1.1