JDBC cache store configuration improvements

The current <jdbc-store ...> element isn't quite explicit enough to differentiate between the 3 types of JDBC cache stores Infinispan has to offer. <string-keyed-jdbc-store ... >, <binary-keyed-jdbc-store ... > and <mixed-keyed-jdbc-store ... > may be better. Similarly, <bucket-table> and <entry-table> expose implementation details. <binary-keyed-table ...> and <string-keyed-table ... > may be better.