Support a Vertex's and Edge's Dictionary Initialization when Creating the Object

[Paebbels]

Currently, a graph's vertex and edge objects can't be initialized with dictionary values, when the object is created. After creation, the dictionary indexing syntax can be used to add new key-value pairs.

Old:

v = Vertex()
v["key"] = "value"

Solution 1:
Use named parameters as initial dictionary values.

v = Vertex(..., key="value")

Solution 2:
Add a new named parameter dict for handing over initial dictionary values.

v = Vertex(..., dict={"key":"value"})