Refactor traefik with package

Split a bit traefik into package. The idea behind this refactor is to
start move inter-dependencies away and do some DRY or SRP.

- Adds a `provider` package, with providers except `web.go`
- Adds a `types` package with common struct.
- Move `gen.go` to an `autogen` package

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

script/binary

@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-if ! test -e gen.go; then
+if ! test -e autogen/gen.go; then
 	echo >&2 'error: generate must be run before binary'
 	false
 fi