Add the possibility to have the same service as source and destination

[fernand0]

Now it is possible to have the same service as source and destination when the type of posts is different. For example, in flickr:

url:https://flickr.com/photos/user
service:flickr
posts:drafts
flickr:fernand0
time:23.9
max:1
hold:no
postaction:

We are publishing drafts (change of state from draft to posts), but it is just a trick in the way publishing is managed.

This can also be done by means of a cache, for example in imgur service:

[Blog20]
url:https://imgur.com/user/user
service:imgur
posts:drafts
cache:imgur
imgur:user
time:23.1 
max:1

This will generate two pairs rule, action. The first one will publish from drafts to a cache, and the second one will publish from the cache to a public post.

We should allow a more general rules management that allows, for example, copying a post from instapaper.com/user2 to instapaper.com/user2