Fixed multiple lines issue of those long questions

- Fixed multiple lines issue of those long questions for
TakeQwizzleViewController and ViewQwizzleViewController
- Fixed the dynamic part, renamed all variables in both
TakeQwizzleViewController and ViewQwizzleViewController
to have the same common name
- Fixed keyboard issue, it's now more smooth than ever!!
- Fixed a bug in the newly added QuizSet's initializer
- Moved all constants into one single header file and have the main
app's prefix file import this file (all controllers now have access to
these constant variables)