Refine OTA system

Now with new command - 'ota_all build_type(in CAPS)'
Before executing 'ota' or 'ota_all build_type(in CAPS)', do 'export MK_OTA_INPUT=/path/to/full/ROM/zip'

Change-Id: I95c86781d23b84e04b3c60a255dfd30ba5125f0f
build: Remove redundant code

'mkdir -p' by default creates all missing folders in given path

Change-Id: I99d28dbc7117c897f2a5bc4318916b912c85044a