GIT-65 Fixed the bignum test

[abidnazirisami]

• Changed the num.has property to a list
• Added a common file to contain global objects
• Modified the num.add function

[abidnazirisami]

• Changed the has from a dictionary to a list
• Took the cfg file to a common.py file (along with eg and fails variables)

Since we were reading from the yml file from every file, the cfg object was in a different state in different file. E.g. the tests.py did not modify the yml file, it just modified the cfg object, but the actual num:add function used a different cfg object (from the num file) that read from the file, ultimately causing the test to fail

• Modified num:add