add max memory for vm configuration (#70)

[yalh76]

Problem

on small memory SBC default java VM memory alocation is too much "3072mb" this result in jvb and jicofo fails to start

Solution

set VIDEOBRIDGE_MAX_MEMORY and JICOFO_MAX_MEMORY in respective config file depends on estimated max user using bridge at a time

[yalh76]

!testme

[yunohost-bot]

Meow :cat2: