1. A system for supporting service level quorum in a data grid cluster, comprising: a plurality of computer servers, the data grid cluster executing thereon, wherein the data grid cluster comprises a plurality of interoperating cluster nodes in the data grid cluster, wherein the data grid cluster supports performing a plurality of services including a root cluster service performed by all of the plurality of interoperating cluster nodes, and at least one other cluster service performed by at least one of the plurality of interoperating cluster nodes specified as a service member of the at least one other cluster service, and wherein the at least one other cluster service provides a different type of service than the root cluster service; a root cluster service quorum policy, wherein the root cluster service quorum policy specifies a minimum number of qualified root cluster service members that are required for performing root cluster service actions of said root cluster service; a cache configuration file associated with the data grid cluster, the cache configuration file accessible to all of the plurality of interoperating cluster nodes and including: a service name element for a first cluster service of the at least one other cluster service that uniquely identifies a name of the first cluster service; and a quorum policy scheme element that contains a reference to a custom action policy for the first cluster service of the at least one other cluster service, the custom action policy specified in a user application; wherein the data grid cluster uses the root cluster service quorum policy to determine whether root service actions are allowed to be performed based on how many qualified root cluster service members are operational in said plurality of interoperating cluster nodes in the data grid cluster; and wherein the custom action policy specified in the user application provides resource-driven control of the first cluster service, wherein the resource-driven control is provided by the custom action policy to the first cluster service via a pluggable interface provided by the data grid cluster and implemented by the user application, and wherein the resource-driven control is based on an external state managed by the user application.