sailfish: allow configuring the startup page

A setting has been added to allow users to select which page should be
opened first. This allows for using Sailfin as a music player
exclusively, as proposed in #34

Special care has been taken to avoid the user being locked out from the
app, for when the library selected as home has been deleted on the
server side. It is real tricky to guide the user to delete dconf keys.

Therefore, a pulley menu with access to settings has been added to all
collection pages and to the unknown page. Additionally, when the setting
is changed, it throws away the entire pagestack and replaces it with the
new home page + the settings page, so the user can always navigate back.
The navigation history of the user will get lost, but otherwise the
implementation gets to complex for a feature that is expected to be used
not that often.

This uses more timers than I hoped for, because otherwise things are
undefined for some reason which I do not know and using timers solves
it. :(

sailfish/qml/Utils.js

@@ -89,7 +89,6 @@ function itemModelImageUrl(baseUrl, itemId, tag, type, options) {
 }
 
 function usePortraitCover(itemType) {
-    console.log("ItemType: " + itemType)
     return ["Series", "Movie", "tvshows", "movies"].indexOf(itemType) >= 0
 }