[WIP] API Update

Hi,

It seems, that the Semantic Scuttle API is not up to date with the [current delicious API](https://github.com/SciDevs/delicious-api). Some new features (like `hashes`) are especially useful for client synchronisation.
With this pull request I want to update the API to be fully compatible with delicious again. It is not finished, but I want to share the progress to allow early feedback.

**Status:**
So far, these API functions have been updated:
 * all new arguments of [`posts/all`](https://github.com/SciDevs/delicious-api/blob/master/api/posts.md#v1postsall), including `?hashes`

**Differences:**
This is a list of functions, which are not fully implemented, because I'm unsure, whether they are usefull:
 * Delicious limits the total possible number of bookmarks returned by ´posts/all´ to 100000. I did not implement any limit.

**Compatibility:**
The changes in the API are mostly backward compatible, as new features are added. I will list the incompatibilities here:
 1. Default Limit: By default only 1000 Bookmarks are returned with `posts/all`. Clients expecting all bookmarks to be returned will not show all Bookmarks (if there are >1000).
 2. Empty results in `posts/all`: An empty result (no bookmarks) now returns `<result code="no bookmarks"/>` instead of an empty `<posts>`-tag.

**About the XML header:**
In delicious the header of the response is `<?xml version="1.0" encoding="UTF-8" ?>` 
In semantic scuttle it is `<?xml version="1.0" standalone="yes" ?>` 
I'm not sure if this is intended or even important. However, I used the header of delicious here.

Cheers,
David