1. A runtime architecture for distributed plug-in configurable middleware for managing distributed applications, the architecture comprising: a plurality of hosts, each host comprising a computer hardware platform; at least one core runtime engine; a plurality of personalities, each personality comprising a definition of a function; a plurality of pre-defined plug-ins, each plug-in associated with one or more of the plurality of personalities and comprising runtime code that provides at least a portion of the function of each personality to which the plug-in is associated and the plurality of plug-ins comprising functional dependencies among the plug-ins, the dependencies comprising relationships among the plug-ins for communicating, cooperating and sharing resources among core runtime engine instances running on the plurality of hosts to achieve the distributed middleware; a plurality of concurrent instantiations of the core runtime engine on the plurality of hosts, each core runtime engine instance comprising sufficient functionality to support plug-in architecture of the pre-defined plug-ins and modified by the pre-defined plug-ins to have personalities associated with those plug-ins, each core runtime instance in communicating, cooperating and sharing resources with other concurrent core runtime engine instances as provided by its associated plug-ins to contribute the functions associated with the personalities associated with the plug-ins used to modify that core runtime instance and to provide the dependencies among the plug-ins in order to establish the distributed middleware within a distributed computing system; wherein each plug-in is utilized by each core runtime engine instance having an associated personality to which the plug-in is associated; at least one configuration manager in communication with each one of the plurality of core runtime engine instances, the configuration manager capable of determining an architecture for the distributed middleware and of distributing plug-ins to the core runtime engine instances; at least one persistent storage device in communication with the configuration manager and comprising the plurality of plug-ins; wherein the host comprises an interface mechanism in communication with the configuration manager to facilitate instantiations of the core runtime engine on the host in accordance with the determined architecture; and wherein each plug-in comprises a core definition comprising instructions for loading and starting the plug-in, a properties section comprising a set of plug-in properties specific to that plug-in and a dependencies section comprising a description of the dependencies comprising the relationships between that plug-in and another plug-in.