Added and changed:

- Added error processing if database is not reachable because of the
connection for example
- Deleted some println and much HTML code inside the servlets. This is
now in the HTML file. Code in servlet only contains welcome message
now, for checking if someone has logged in or not. This is done for
preventing spaghetti code.
- Replaced some println and HTML code with Strings for giving through
the Velocity context.

- Added customer Java Bean for keeping the data for the customer (if
needed in a later stadium). Still in dev.