WIP: Migrate stratux dependencies from git-modules to Go modules

[doodles526]

This PR is a WIP for moving dependencies away from git-submodules and onto Go's module system which is considered stable as of 1.14. Note: this would bump the required Go version up to 1.14 as well.

I am yet to test the new code-base on the rPi - but I am successfully building the binaries now. Note: this depends on changes to goflying as well. Link to that PR will be added upon its creation.

[doodles526]

Depends on https://github.com/cyoung/goflying/pull/1