Alpha Pre-Release v1.7.2

add docker merge sub-command for merging the layers of both local docker images and images downloaded from docker hub.

lpmx docker merge image:tag

it will automatically generate a new image with only one layer named image:tag-merge

Notice:
from this version for volume mapping parameter, please change to use the following format:

lpmx docker create -v host_path1=container_path1:host_path2=container_path2 image:tag