Add proxyserver gatekeeper middleware

swift::proxy::gatekeeper class will be used to configure
gatekeeper middlerware.

Change-Id: I2f90ae41ba98f9b7d2bd7f3c5ed92fdbcd8fa999
Implements: blueprint icehouse-proxyserver-middlewares
Add swift::proxy::slo class

swift::proxy::slo class is used to configure proxy slo middleware.

Change-Id: Ic751d2e89de39478b55e3323ddf220610b1b7541
Implements: blueprint icehouse-proxyserver-middlewares
Add client_package_ensure parameter and swift::client class

In the actual state of the manifest we can only setup package_ensure to
absent|present|latest. This commit allow end users to pin swift* and
swift-client to a specific version. (note that swift* and
python-swiftclient version are not the same).

A new class (swift::client) manage now client packages, and we keep the
retro-compatibility of commit 020b7723cbbe75fbcae89514a1e1882ae807fb27.

Change-Id: I9bcc5a0f9d0a93a812fb574c4571fb9584077e4a
Merge "Add client_package_ensure parameter and swift::client class"
Merge "Add swift::proxy::slo class"
Merge "Add proxyserver gatekeeper middleware"