refuse to run without project_id set

[displague]

The current behavior is dangerous:

WARNING: 2021/02/21 21:31:54 main.go:45: Could not list devices GET https://api.equinix.com/metal/v1/projects/devices?include=facility: 404 Not found 
WARNING: 2021/02/21 21:31:55 main.go:58: Could not list vlans GET https://api.equinix.com/metal/v1/projects/virtual-networks: 404 Not found 
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x697330]

goroutine 1 [running]:
main.main()
	/code/main.go:61 +0x4b0