vndk-def: Add symbol data in VTool

Using the command "dep-graph" the tool find the symbols information
between two libs and show the dependency symbols list

Test: Run `vndk_definition_tool.py dep-graph \
	--system ... --vendor ... -o "html_output" \
	--tag-file "[vndk_tag_table].csv"'

Change-Id: Ie7eb33d9227dc2454330049c3edf8bcb77358e2f