docs/platforms/sim/sim/boards/sim: Clean up legacy SIM documentation.

Migrate README.txt about ROMFS to SIM documentation in RST format. Also
cleans up the formatting of the board documentation to leverage RST's
features.

Signed-off-by: Matteo Golin <matteo.golin@gmail.com>

Documentation/platforms/sim/sim/boards/sim/README.txt

@@ -1,120 +0,0 @@
-README
-======
-
-  Overview
-  --------
-  This directory contains logic to support a custom ROMFS system-init script
-  and start-up script.  These scripts are used by by the NSH when it starts
-  provided that CONFIG_ETC_ROMFS=y.  These scripts provide a ROMFS volume
-  that will be mounted at /etc and will look like this at run-time:
-
-    NuttShell (NSH) NuttX-12.10.0
-    nsh> ls -Rl /etc
-    /etc:
-     dr-xr-xr-x       0 .
-     -r--r--r--      20 group
-     dr-xr-xr-x       0 init.d/
-     -r--r--r--      35 passwd
-    /etc/init.d:
-     dr-xr-xr-x       0 ..
-     -r--r--r--     110 rcS
-     -r--r--r--     110 rc.sysinit
-    nsh>
-
-  /etc/init.d/rc.sysinit is system init script; /etc/init.d/rcS is the start-up
-  script; /etc/passwd is a the password file.  It supports a single user:
-
-    USERNAME:  admin
-    PASSWORD:  Administrator
-
-    nsh> cat /etc/passwd
-    admin:8Tv+Hbmr3pLVb5HHZgd26D:0:0:/
-
-  The encrypted passwords in the provided passwd file are only valid if the
-  TEA key is set to:  012345678 9abcdef0 012345678 9abcdef0.  Changes to either
-  the key or the password word will require regeneration of the nsh_romfimg.h
-  header file.
-
-  The format of the password file is:
-
-    user:x:uid:gid:home
-
-  Where:
-    user:  User name
-    x:     Encrypted password
-    uid:   User ID (0 for now)
-    gid:   Group ID (0 for now)
-    home:  Login directory (/ for now)
-
-  /etc/group is a group file.  It is not currently used.
-
-    nsh> cat /etc/group
-    root:*:0:root,admin
-
-  The format of the group file is:
-
-    group:x:gid:users
-
-  Where:
-    group:  The group name
-    x:      Group password
-    gid:    Group ID
-    users:  A comma separated list of members of the group
-
-  Updating the ROMFS File System
-  ------------------------------
-  The content on the nsh_romfsimg.h header file is generated from a sample
-  directory structure. You can directly modify files under etc/ folder,
-  The build system will regenerate nsh_romfsimg.h automatically.
-
-  See the sim/nsh configuration for an example of the use of this file
-  system.
-
-  Replacing the Password File
-  ---------------------------
-  The sim/nsh configuration can also be used to create a new password file.
-  First, make these configuration changes:
-
-    1. Disable logins
-
-       - CONFIG_NSH_CONSOLE_LOGIN=y
-       + # CONFIG_NSH_CONSOLE_LOGIN is not set
-         # CONFIG_NSH_TELNET_LOGIN is not set
-
-    2. Move the password file to a write-able file system:
-
-       - CONFIG_FSUTILS_PASSWD_PATH="/etc/passwd"
-       + CONFIG_FSUTILS_PASSWD_PATH="/tmp/passwd"
-
-    3. make the password file modifiable
-
-       - CONFIG_FSUTILS_PASSWD_READONLY=y
-       # CONFIG_FSUTILS_PASSWD_READONLY is not set
-
-  Now rebuild the simulation.  No login should be required to enter the
-  shell and you should find the 'useradd', 'userdel', and 'passwd' commands
-  available in the help summary, provided that they are enabled.  Make
-  certain that the 'useradd' command is not disabled:
-
-      # CONFIG_NSH_DISABLE_USERADD is not set
-
-  Use the NSH 'useradd' command to add new uses with new user passwords like:
-
-    nsh> useradd <username> <password>
-
-  Do this as many times as you would like.  Each time that you do this a new
-  entry with an encrypted password will be added to the passwd file at
-  /tmp/passwd.  You can see the passwd file like:
-
-    nsh> cat /tmp/passwd
-
-  When you are finished, you can simply copy the /tmp/passwd content from the
-  'cat' command and paste it into an editor.  Make sure to remove any
-  carriage returns that may have ended up on the file if you are using
-  Windows.
-
-  Then recreate the nsh_romfsimg.h file as described above.  In step 2,
-  simply replace the old /etc/passwd file with the one in your editor.
-  When you are finished, the new passwd file will be in the ROMFS file
-  system at the path /etc/passwd.  When you restore the original NSH
-  sim configuration, these are the passwords that will be used.