Change schema to better known naming convention

This proposal changes the schema of the knowledge base to be more in line with known programming languages.

Changes:
* `<rule><when/><then/></rule>` becomes `<rule><if/><then/></rule>` and the `<if>` element has to contain a single top level condition element (`<and>`, `<or>`, `<not>` or `<fact>`.)
* `<when_all/>` becomes `<and/>`.
* `<when_any/>` becomes `<or/>`.