Path semantics for UHS.

UHS style will follow ace style when referencing separate drives/partitions.

UHS style while in single-root mode:

cd :path/to/file 
     The : at the beginning indicates (amiga-style) that it
     starts at the root of the filesystem.
     

cmd style:

<part>:/<path>

     Since CMD's devices are designed to work independently to one another,
     there's no organized way to deal with device numbers in the cmd @cd
     command.  Having this style in here at all is only for the convenience
     of CMD device owners.

     CMD relaive paths either start with the directory name, or with a /. 
     That's why UHS style on single-root was set up amiga-style.

ace style:
<dev>:<part>/<path>

     ACE was designed as an overall easy-to-use environment, and as such
     needed a convenient way to change devices et.al from within a shell
     script. There we have it.
     
     The presence of the : in the path specifies that it's a full path. ;)

    
-=-

It's possible to easily auto-detect and implement these with the same chunk
of code.  Relative paths are easy enough to decode, since they're the same
for all three syntaxes.  

Detecting an ace path against a cmd path is easy.  Look for a
number between the : and the / in the path.  If there's nothing between
them, its cmd style.  If there is, it's ace style.  Note: UHS will allow
specifying the partition by name.

<Nate\DAC> and I have discussed the CMD's save-path-for-partition feature. 
This will also need to be implemented (and was planned to some extent).




-- definitions --

<dev>          : An integer pointing to a kernel device ID
<part>         : An integer pointing to a partition ID in current (or
                 specified) device
<path>         : A unixish path (see root-path)
<root-path>    : A path from root (i.e. /file/from/root)