Core: Show all templates initially, remember platform choice

Signed-off-by: Martin Kampas <martin.kampas@jolla.com>
(cherry picked from commit 78d594c93ee4ce2436336287db4964f36549aaff)
Add preferredFeatures support to wizards

Signed-off-by: Martin Kampas <martin.kampas@jolla.com>
(cherry picked from commit e6cadea29b7588866e5b42ff78f31628cc2e4c76)
Add preferredFeatures support to examples

Notice how it deals with 28e5eea (Example launcher: Don't configure kits
automatically)

Signed-off-by: Martin Kampas <martin.kampas@jolla.com>
(cherry picked from commit cad03e960cd5feb004b42da58132b058c77b8823)
Add platform and preferedFeatures support to tutorials

Signed-off-by: Martin Kampas <martin.kampas@jolla.com>
(cherry picked from commit 3e6e8990fbbbeeff2a9c32df1013bdaf36778eef)