Add File Handling Class

The class is responsible for handling File I/O. The inputs are text
files containing the numbers to be averaged.
Make function visible

Also functional in more than one case.
Remove unused file
Test code for new FileIO class
Elevate app permissions
C# assumes everything as public
Fix bug

Person tought C# assumes everything public
Fix array error.

An array erroy prevented the program from functioning correctly.
Catch when file does not exist

When file does not exist, or no file is specified, enter manual input
mode.
Make instrucctions simpler

Rewrite the instructions showed to the user. Now they are more clear and less vague
Merged in File-Reading (pull request #1)

Add file handling capacities to program