PKI and PKIZ tokens unnecessary whitespace removed

In the race to produce smaller PKI tokens, we've overlooked
that we can produce smaller JSON bodies by removing all whitespace
between structural characters.

This patch offers a solution by overloading
item_separator and key_separator in class SmarterEncoder
used to produce json response.

Change-Id: Id7fcc82a28359e85feac57f9469f2bcd9192ee50
Closes-Bug: #1348262
Merge "PKI and PKIZ tokens unnecessary whitespace removed"