Define well-known public-append basic ACL

[alexvanin]

There is a demand for public containers that are free for writing but are locked for deleting. Users tend to use well-known public-read-write basic ACL, but it requires restrictive extended ACL with a bearer token control of the user actions. It's a bit complicated for the newcomers.

Instead I propose to define public-append basic ACL constant. Container owner stays in charge of the data control, but other users cannot delete any objects, so data won't be lost "accidentally".

0x1FBF8FFF

+-----------+--------+-----+
| OPERATION | TARGET | BIT |
+-----------+--------+-----+
|           | Sticky |  0  |
+-----------+--------+-----+
|           | Final  |  1  |
+-----------+--------+-----+
| RANGEHASH |  User  |  1  |
+           +--------+-----+
|           | System |  1  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+
|   RANGE   |  User  |  1  |
+           +--------+-----+
|           | System |  0  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+
|  SEARCH   |  User  |  1  |
+           +--------+-----+
|           | System |  1  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+                
|  DELETE   |  User  |  1  |
+           +--------+-----+
|           | System |  0  |
+           +--------+-----+
|           | Others |  0  |
+           +--------+-----+
|           | Bearer |  0  |
+-----------+--------+-----+
|    PUT    |  User  |  1  |
+           +--------+-----+
|           | System |  1  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+
|   HEAD    |  User  |  1  |
+           +--------+-----+
|           | System |  1  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+
|    GET    |  User  |  1  |
+           +--------+-----+
|           | System |  1  |
+           +--------+-----+
|           | Others |  1  |
+           +--------+-----+
|           | Bearer |  1  |
+-----------+--------+-----+

I am not sure whether bearer token bit should be set for DELETE or not.

This change should be reflected in neofs-spec.

/cc @realloc @cthulhu-rider @carpawell

[alexvanin]

Closed in #347