DFS can have its first vertex specified.
Utility method
Tree verification
Excludes
Merge branch 'noscala'

Conflicts:
	gga.iml
	src/main/java/org/gga/graph/impl/FilteredGraph.java
	src/main/java/org/gga/graph/impl/SparseGraphImpl.java
	src/main/java/org/gga/graph/search/bfs/ParentRecorder.java
	src/main/java/org/gga/graph/search/dfs/DepthFirstSearch.java
	src/main/java/org/gga/graph/search/dfs/Dfs.java
Merge remote-tracking branch 'origin/master'

Conflicts:
	gga.iml
Project files update.