- Alter TubeLines.xml to be simpler through inlining tags. Use lines as
xml root, line as elements and station as sub elements 
- use properties of the annotations to map TubeLines to lines, TubeLine
to line and inlining the element list as well as inlining the Station
element list
- clean up encapsulation of variables and formatting of classes
- add assert statements to the test case to ensure that xml file has
been read in correctly
- read in xml file using resource location methods rather than hardcoded
string paths.