Add JavaDoc for the other getter of keyboardLayout

Information about the keyboardlayout variable being a comma-separated String
is added to the JavaDoc.
Add constructor that accepts row to be used as primary key

The constructor adds a constraint to the table about what column to use as the
primary key.
Fix formatting

Unnecessary new lines were deleted.
Use BIGINT for IDs

The data type of the IDs are changed to BIGINTs because they are `long`
variables.
Implement method that adds new record to the database

Test for whether or not there are runtime errors has also been done in the Tester
class.