#44 Remove dependency on commons-config

[Stephen Starkey]

The entire commons-config library is 200 MB. The amount of code that beankeeper uses is tantamount to 10 lines. Replace commons-config with a simple properties file loader. We have already ripped out the dependency by providing our own custom classes:

org.apache.commons.configuration.Configuration
-- only provided the getInt method

org.apache.commons.configuration.PropertiesConfiguration
-- only provided the getInt method

org.apache.commons.configuration.AbstractConfiguration
-- only provided addConfigurationListener and removeConfigurationListener

org.apache.commons.configuration.event.ConfigurationListener
-- didn't provide any methods