[wsrp] Issue #39: Default value forServiceDescription.supportsExportByValue

[Rich Thompson <richt2@us.ibm.com>]

Issue # 39
Spec section: 
SubCommittee: Interfaces
Owner: Andre
Description:
Should not the expected value of supportsExportByValue
be true if exportPortlet is supported. This clashes with the "default"
needing to be false if exportPortlet is not supported. Maybe better to
make this field optional rather then defaulting it (better backwards compatibility).
Note it has an [O].