Add routes priorities

[emilevauge]

This PR adds routes priorities to avoid path overlap.
By default, routes will be sorted using rules length:
PathPrefix:/12345 > PathPrefix:/1234 > PathPrefix:/1
You can customize priority by frontend:

  [backends]
    [backends.backend1]
      [backends.backend1.LoadBalancer]
        method = "wrr"
      [backends.backend1.servers.server1]
      url = "http://172.17.0.2"
      weight = 1
    [backends.backend2]
      [backends.backend2.LoadBalancer]
        method = "wrr"
      [backends.backend2.servers.server1]
      url = "http://172.17.0.3"
      weight = 1

  [frontends]
    [frontends.frontend1]
    backend = "backend1"
    priority = 10
    passHostHeader = true
      [frontends.frontend1.routes.test_1]
      rule = "PathPrefix:/to"
    [frontends.frontend2]
    priority = 5
    backend = "backend2"
    passHostHeader = true
      [frontends.frontend2.routes.test_1]
      rule = "PathPrefix:/toto"

• code
• tests
• doc

Fixes #298

Signed-off-by: Emile Vauge [email protected]

[vdemeester]

LGTM 👍