[BUG] Crash on exporting/saving multiple pointclouds

[state-of-the-art]

Issue description:

Application crashed when there is too much pointclouds are displayed (~18-20) or it's trying to save/export a huge amount of the shots.

Environment:

• Application version: 0.5.1
• Device: Samsung Galaxy S8 SM-G950U1
• OS: Android 7.0 Nougat
• Camera: Intel Realsense D415

Steps to reproduce:

Steps to reproduce the behavior:

1. Run the Handy3DScanner
2. Connect d415 camera
3. Capture 30 pointclouds
4. Go to Edit tab and enable the clouds one-by-one
5. Eventually the application will crash

Expected behavior

We need a proper memory management, because pointclouds operations are quite memory-hungry. So the first step - we need to monitor the available memory to let the user know how much shots could be processed. Second step - is to offload the not-active shots to disk and load them if they are needed.

Overall all the captured shots should be mapped to disk to make sure none of them will be lost.