Please document EE_DISABLE_AUTO_CHECK_UPDATE and EE_AUTO_CHECK_UPDATE_DAYS env vars

Hello

Please put in the doc a note about disabling auto-update, we incurred in many crashs after auto-update, so we needed to disable the auto-update mechanism

The problem is auto-update prompt randomly appears and some people inadvertently hit the enter key ! Our production machine went down for a day !

# YOU MUST BE CRAZY to LEAVE AUTO-UPDATE TURNED ON !!!

I used EasyEngine on many servers since 10 years, and the auto-update features is not 100% safe, you always need to take a snapshot before run in case of a disaster...