Docs update

There goes the first round of the docs update. I tried to make the examples work and I think I succeed. I wrote some code to create the necessary tables using jdbc but I'm not sure about where it should go. So if you type the examples top to bottom and has the tables they should work (at least they do for me). There is one exception. The second transaction example has a (valid?) function but I don't know how to write it.

There are some functions in the docs that left me clueless about how to use them in a practical way:
* from
* post-query
* sqlfn*
* where*
* having*
* query-only
* create-entity

If you have some examples, I would be glad to update again.

Let me know if I need to change something.