#216 primary key generation support

[Alexey Loubyansky]

Entity element is allowed to have entity-command
element of the form:
<entity-command name="CommandName"
class="ComandClass">
<attribute name="attr1">value1</attribute>
<attribute name="attr2">value2</attribute>
</entity-command>

where only name attribute is required; others are subject
to override.

The commands were introduced to support different
ways of creation primary values for entities.

The list of available commands specified in entity-
commands elment in standardjbosscmp-jdbc.xml. The
default command is specified in standardjbosscmp-
jdbc.xml in defaults element.

Each entity can override the entity-command in defaults
by specifying its own entity-command.

The role of overriding:
- entity-command's in entity-commands element contain
a full command setup;
- entity-command in defaults can override class or each
attribute of the command in entity-commands by
supplying 'class' or 'attribute' element;
- entity-command in entity element can override entity-
command in defaults or the one in entity-commands
element.

Also a new element <auto-increment/> now available in
cmp-field element.