[jvstm-common] Add StandaloneVBox
Create backend jvstm-datagrid

This backend adds support for running JVSTM on top of a (pluggable) data
grid.  It also includes an implementation for Infinispan.

E.g to use the Infinispan data grid one should provide the following
configuration:

    config.class=pt.ist.fenixframework.backend.jvstm.datagrid.infinispan.DataGridConfig
    dataGridClassName=pt.ist.fenixframework.backend.jvstm.datagrid.infinispan.InfinispanDataGrid

And optionally:

    dataGridIspnConfigFile=<the-ispn-config-file>
[jvstm-common] Implement StandaloneVBox.reload() and makeNew()
[jvstm-datagrid] Update Repository implementation