SdkManager: suggest which platform to install to fix a broken addon.

SdkManager: suggest which platform to install to fix a broken addon.

The SDK Manager now has the notion of a "broken installed package".
The BrokenPackage can specify that:
- it requires a certain minimal platform to be installed,
and/or:
- it requires a specific exact platform to be installed.

The later constraint is expressed by IExactApiLevelDependency and
allows UpdaterLogic to find which platform would fix an addon which
is missing its base platform.

Change-Id: If429ea39f0ddc19c0cb906bf6766df310de28981