slapos_jio,slapos_erp5: move WebSection_getHostingJSPrecacheManifestList from slapos_hal_json_style to slapos_base portal_skins

this script is needed to generate translation data so it must be in a
directory available in all skin selections

slapos_accounting: In case of Subscription, generate invoice 15 days earlier them begin of the next period.

After 1.6.1 was deployed we have two processes, stop the redundant process.

In 58fbaabf (svcbackend/standalone: use shorter names for supervisor sockets
, 2020-07-17) we changed the socket path from supervisord.sock to a shorter
sv.sock, but this caused issues when updating running slapos node instances,
because this was trying to start a new supervisord process using the new
socket path, while the old one was still running.

To keep services running after upgrade, introduce a compatibility layer in
this socket path - if we still have a supervisord running with a socket at
this previous path, keep using this old socket name.

Output is already captured on SlapPopen instances and the output
is available with output attribute.

    User can view his Cloud Contract and its consumption.

      This is used to Sales website when a Invitation token is provided and it will be used when request button will be available on logged user website.

    This consider Maximum Delay and Maximum Credit a user can have

   This is a faster version to later accomodate custom implementation from Cloud Contracts

    This help us to avoid query outdated catalog, consider that the user is only at transaction for now.

  This requires more work before continue.