Formatting changes and spelling errors corrected

[kpchi]

1. Multi-line comments are now formatted as follows:
   """
   Text
   """

2. Single-line comments are now formatted as follows:
   ' # Text

3. TODO Sections are now standardised and formatted as follows:
   ' ## ADD CODE HERE

4. For all written answer questions, TODO is now standardised and formatted as follows:
   """ TODO: Your answer HERE """

5. Miscellaneous spelling errors have been corrected

[gdanezis]

I will review and merge -- many thanks for all the typos!

[kpchi]

Hi @gdanezis, just wondering if you had the time to review the changes?