Setting version to 0.7.0:

* A lot of general code refactoring (most of it in #62):
    - Setters return the subject for chaining calls
    - Added arity-specific methods in/out-E/V methods with default implementations
    - Moved all the methods from TypedGraph to the elements interfaces
    - Split Arity on two: From/To; Added FromArity to Property
    - Added Unique and NonUnique Property types to fix the arity
    - Added vertex/edge types list to the typed graph and properties list to each typed element
    - Added UntypedGraphSchema interface for automatic schema creation
* See also #46, #51

version.sbt

@@ -1 +1 @@
-version in ThisBuild := "0.7.0-SNAPSHOT"
+version in ThisBuild := "0.7.0"