SQLiteDatabase: Added database class and table creation

The SQLiteDatabase class will be a database that uses SQLite 3 to store and query activities.

Code that connects to the database and creates the main table when needed is present.
SQLiteDatabase: Added method to insert entries

Added a method to insert entries to the main table.
SQLiteDatabase: Added various methods for adding activity entries.

Implemented the methods to add the no change, modification and deletion entries.
SQLiteDatabase: Added method to get most recent entry of a file

The method looks up the most recent information in the main table for a given file.
SQLiteDatabase: Added shouldUpdate method

Implemented the method that checks whether a file should be updated.
SQLiteDatabase: Track encountered files

Added tracking of the encountered files. This will be used to decide which files were removed since the last backup.
SQLiteDatabase: Handle removed files

Implemented the method to handle removed files and register them in the database.
SQLiteDatabase: Fix path of the database file

The database file should reside in the root of the backup structure, not in the current working directory.
Backup: Added testing code for SQLiteDatabase

Using SQLiteDatabase as the default now. Should be configurable in the future.
SQLiteDatabase: Changed main table creation routine name

Changed the method to create the main table to make clear it creates the main table.
SQLiteDatabase: Added creation of the info table

The info table contains the version of the backup utility used to create the backup.
Version: Added version information for the SQLite database

The version information for an SQLite database type is used to check if database types of future databases will be compatible with older storage mechanisms.
SQLiteDatabase: Store the SQLite database version

The SQLiteDatabase class now stores the SQLite database version in use when creating the info table.
Version: Fixed variable name typo
Version: Added method to check compatible SQLite versions

The method checks whether a SQLite database version is compatible with the current version.
SQLiteDatabase: Added method to check the database version

The method checks whether the used database version is compatible with the application.
SQLiteDatabase: Added incompatible version exception

The SQLiteDatabaseVersionException is raised when an incompatible database version is detected.
SQLiteDatabase: Raise exception for incompatible database versions

The method that checks the versions now raises an exception an is called when connecting to the database.
Configuration: Changed option names to lowercase

Changed the source and destination options to lowercase as it is specified in the documentation.
Configuration: Added database type option

Added database type option which specifies which database type to use when storing metadata about the backup.