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 |   60 MB | previously used as /cache  |
| /cache      | /dev/block/mmcblk0p15 |  535 MB | previously used as /system |
| /system     | /dev/block/mmcblk0p17 |  1.0 GB | previously used as /data   |
| /data       | /dev/block/mmcblk0p28 |  1.7 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.
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