ramdisk: Change the assignment of partitions and use an emulated sdcard

Since there isn't available space inside /data and /system partitions, we must
redistribuite partitions and use internal sdcard space as data partition.
The new partitions configuration is the following:

| Mount Point | Device                |  Size   | Note                       |
|----------------------------------------------------------------------------|
| <not used>  | /dev/block/mmcblk0p16 |   94 MB | previously used as /cache  |
| /cache      | /dev/block/mmcblk0p15 |  552 MB | previously used as /system |
| /system     | /dev/block/mmcblk0p17 | 1.33 GB | previously used as /data   |
| /data       | /dev/block/mmcblk0p28 | 4.98 GB | previously used as /sdcard |

The internal sd card will be emulated (emulatedsd) and will share data partition space.
prop: Use /cache partition to store dex files of system apps

By doing so we can free up some space of /data/dalvik-cache used by
system apps. The dalvik cache of system apps will be stored inside
/cache partition, which has a bigger size (552MB) after the partition
reassignments.
prop: Set MTP as default USB interface

Mass storage seems to be not well supported, external sd card is unmounted
by the system when you try to connect the USB cable.
config: Add USB audio support