Parameter deprecation support

This patch adds implementation of parameter deprecation system.
Packstack will now check for deprecated parameters in answer file
if current parameter is not found in answer file.

Also support for default values have been added. Eg. when parameter
is not found in answer file, Packstack tries to use default value
instead of throwing exceptions. This will allow smaller answer files
where only few parameters have to differ from default values.

Change-Id: Id646a442e789221e5c31c9c151bcdfd118652e8f