Cleaned up 'using' statements in Ex3_2.
Single lines following 'if'/'for' now in braces

Reduces the fragility of the code.
Updated Ex3_1 and Ex3_2 for better readability
Removed redundant comment from Ex3_4
Updated Ex4_1 for better readability

Expanded single Console.Write() call to multiple Console.Write().
Updated Ex4_3 for better style

Removed redundant comments and renamed fields.
Updated Ex4_4 for better style

Removed redundant comment and included 'args' argument to Main() method.
Updated Ex5_1 with better variable names

Now use 'counter' rather than 'i', and removed the magic number 10,
replacing it with a constant.
Updated Ex5_2 for correct program flow.

'inputInt' is now tested to see if it's a multiple of 10 before even and
odd, as multiple of 10 => even. Therefore, only one message is printed for
each input.
Updated Ex5_3

Ex5_3 now performs correctly (as with Ex5_2), and is now more readable
(removed nested ternary operator, InputType is now determined using an if
statement).
Updated Ex5_4 with 'args' paramater in 'Main()'
Updated Ex7_1 for better style

Altered variable names in Math.cs and Program.cs, and also added 'args'
parameter to Main() method in Program.cs.
Updated Ex7_2 for better style

Made Math a static class to prevent it being instantiated in error. Also
performed style updates as in the update to Ex7_1 (variable names and
'args' parameter).
Updated Ex7_3 to use 'string' rather than 'String'
Updated Ex7_3 for better style

Renamed ISBN -> isbn to follow naming conventions, and added 'args'
parameter to Main() in Program.cs. Also removed unnecessary usage of
'this' in Book.DisplayBook().
Updated Ex7_4 for better style and readability

- Now uses 'string' rather than 'String' when appropriate
- Drawing algorithm in Square.cs rewritten for clarity
- Variable names altered throughout for clarity