Description Class constructor. Create a new instance of an MStringResourceId.
This object can then be used to register and retrieve MStringResource's. The unique resource key is formed from a pair of strings: the
name of the plugin the string is associated with and a unique Id
for this particular string. The resourceId also contains the string's
default value. Arguments
pluginId the name of this plugin
keyString the unique string Id (within this plugin)
defaultValue the default value for the string resource