Armory's installer should ask where to save the data directory

[fresheneesz]

Most of the storage space for Armory is obviously the blockchain database (tho i'm not sure why it needs a separate one from bitcoin core's database). The installer asks where the program should be installed, but it doesn't ask about the database. Its useless to put the database and program on different disks, but the only way to change what disk to put the database on is to set a comand line flag. This should be doable via the installer, so people can manage their disk space better.