Replace deprecated has_key method

This patch replaces the deprecated 'has_key' method for dictionaries
and uses the 'in' keyword instead.
Merge pull request #3 from vmrob/deprecated

Replace deprecated has_key method
Touch up parentheses and make use of new Class.size variable
Initial work on adding thrusters, gyros, and reactors
Remove initialization globals

This patch removes the initialization variables and provides a more
Pythonic initialization mechanism. As the scripts are executed during
the import, it's sufficient to run the initialization functions in the
relevant scripts instead of relying on global initialization
variables.