Now showing properly set info

-> SetInfoActivity now shows image / building instruction button /
description / year / price / number of pieces
-> Image loads using ImageLoader with a spinner when downloading
-> Created SetInfo class to set/get info about a specific set
-> TulpApplication class returns (fake) set info from specified setId,
in the futur this method will be modified to use the database
-> Added strings
-> Created res/values/plurals.xml for the number of pieces which varies
from 0, 1 and other (but 0 case is ignored, using another string
instead)