- software catalog now has a list of variables included

 Changes to be committed:
	modified:   src/domain/model/software_catalog.py
	new file:   src/domain/model/variable.py
	new file:   src/domain/parse/variable_parser.py
	modified:   test/domain/model/test_package.py
	new file:   test/domain/model/test_variable.py

Changes:
	new file:   test/domain/parse/test_variable_parser.py

Added custom error MalformedVariableError

 Changes:
	modified:   src/domain/parse/variable_parser.py
	new file:   src/exceptions/malformed_variable_error.py
	modified:   test/domain/parse/test_variable_parser.py

Changes:
	new file:   src/database/__init__.py
	new file:   src/database/database_connection.py
	new file:   src/database/variable_table_creator.py
	new file:   test/database/__init__.py
	new file:   test/database/test_variable_table_creator.py