Changes:

1) Added "msgpub" to the list of API calls. An example of usage follows:
api.msgpub("TESTSIMCLOUD","VM","channel name","some message").

2) Added "hostalter" to the list of API calls. Usage exactly identical to other
*alter (e.g., vmalter, aialter) calls.

3) Users can now replace attributes on objects through a msgpub API call. For
instance, attaching a vm with "vmattach tinyvm auto empty iron32
pause_provision_started async" would cause the VM to pause and wait for the user
to publish a message. At this point, the user could run its own custom placement
engine mechanism and then communicate its decision back to the VM with an API
call like api.msgpub("TESTSIMCLOUD", "VM", "staging",
"vm_2;continue;host_name:simhosta1"), effectively overriding the cloud's
placement engine. Evidently, the cloud has to provide support for placement
engine overriding (e.g., OpenStack).

4) The coremark Virtual Application type has now the number of operation
determined by the combination of the parameters LOAD_LEVEL*LOAD_FACTOR.

5) Several simplifications and improvements for the *ycsb Virtual Application
types (i.e., redis_ycsb, cassandra_ycsb, mongo_ycsb), including a new parameter
RECORD_SIZE.