Version 20170710 with hwaccel for rpi

Based on ccrisan's version 20170710, but with hwaccel for Raspberry Pi. More information about hwaccel here motioneye-project#365.
This is completely untested and highly experimental. Use at your own risk.

Minimum hardware requirements: 512MB RAM
If you have the 256MB RAM Raspberry Pi, please use the previous pre-release.

To get the optimum movie quality, tune the following:

• resolution
• fps

Pi Zero W recommended configuration:

• GPU memory: 96M
• Resolution: 1280 x 720
• Frame rate: 20 fps
• Movie format: H.264 (mp4 or mkv)
• Pre-capture: maximum of 20 frames (higher pre-cap uses more RAM)
• Minimum motion frames: 15 frames (higher value uses more RAM)
• No web browser connection as it consumes too much CPU.

Pi2 and Pi3 are able to run at higher resolution, but need 128M of GPU memory. Use gpu_stat script to check available GPU memory.

Known issues / limitations:

• Raspberry Pi with 256MB RAM is no longer supported due to its limited memory.
• Wifi stops working after first boot when connecting to certain access points. Workaround here: motioneye-project#1012
• Fails to create movie previews.
• Movie quality in configuration does nothing.

Changes:

• Log files are stored in RAM to reduce microSD card wear.