Added ability to list devices to API
Ticket #16: Ability to set expiration date as voucher code

Tried to fix Ticket #15 by disable caching - will start lab session now to see if it works
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Logical failure made it impossible to use expiration dates for voucher codes.

Updated version number.
Merge pull request #24 from litzi0815/V-0.4.3

V 0.4.3