Refactor problem calling code

Created a macro to make adding new problems easier.
VS solution update
Add Problem18 outline with initial graph construction - no solution
Begin using boost graph library for Problem 18
Complete Problem 18 for example weights
Finished BGL implementation, but wrong answer :(
Complete Problem 18

Learnt how to use boost graph library :)
Merge branch 'Problem18' into development
Update Readme
Merge branch 'development'