Load methods from method manifest

Methods are now loaded from the method manifest. Created
new ZSZuseDSL (stands for Domain-Specific Language)
class which holds the canonical forms of statements and
expressions that the editor understands.
Merge pull request #73 from ZuseApp/method-manifest

Load methods from method manifest
Galaga mostly working (but crashing)

Fixed Galaga JSON so it can be listed amongst the demo
projects, but we don’t support the `every` statements
properly so it crashes in the editor.
Merge branch 'master' into edit-toolbar
Fixed Galaga JSON.