An Execute packet is sent by the client to request execution of a cursor/portal.
The packet object has the following methods:
String getPortalName() : gets the name of the portal/cursor to execute. This can be an empty string for the default portal.
void setPortalName(String name) : sets the name of the portal to execute.
int getMaxRows() : gets the maximum number of rows to return. Zero means no limit.
void setMaxRows(int n) : sets the maximum number of rows to return. Zero means no limit.