[1/2] Camera: add software HDR rendering

This allows devices without HDR camera (so all phones except Nexus 4
I think...) to actually take HDR pictures. When the mode is enabled,
pressing the shutter button will take 3 shots, one a minimal exposure,
one at 0 exposure, and one at max exposure. The 3 shots are then fed
into a software HDR processor that will merge the 3 images into one
final shot.

There are two algorithms available for merging pictures, one is a
simple average between all pixels, and the second one is based on
Reinhard's algorithm. They all need tweaking, and only the first one
is used for now.
Average algorithm is available in RenderScript form. This beastie
speeds up a lot!

Source shots are removed after HDR is computed

Change-Id: I7a9e52e56258a0c755f4def22db51ac84501ce9a
camera: Add options to better control video preview size

 * usePreferredPreviewSizeForEffects is needed to fix camcorder effect on
   some MSM8660 devices.
 * Add ignorePreferredPreviewSizeForVideo to use the best size reported
   by the driver instead of the preferred-preview-size-for-video value,
   which may report something really awful.

Adapted for cm-10.1 from similar commits in jellybean.
  https://github.com/CyanogenMod/android_packages_apps_Camera/commit/5ea90585dfce5a38f0c91d2ae07145770a0ea569
  https://github.com/CyanogenMod/android_packages_apps_Camera/commit/7310af07d00910033adbd2dce6aaf8b04cd1f220

Change-Id: I58d4f81333a26dbd6d1ce35037b9c32fbd7d5b69
Camera: SoftwareHDR: Reduce mem usage and let exposure time get tuned

- The memory usage has been reduced. Instead of doing 3 bitmaps and
  keeping them in memory, only one bitmap is used and recycled once
  copied to the renderscript allocation.
  In counterpart, I had to remove the software (non-RS) processing.
  I haven't seen any issue of devices disliking RenderScript, so
  I think it's fine.

- I added a config overlay to set the exposure settle time between
  the shots. Some devices are faster than others (ZSL devices can
  take less than 1 second, the previous value). I set this to 0.8
  seconds by default, which works fine on i9100/n7000.

Change-Id: Ia067b717a3754ffb423b29a915d2ae411d04f0b9