Notes on URLs

     The URL will be for a file that is a *.tek file.  We will grab it,
     saving the URL so that we can install other files.

     Another type of URL will be a table-of-contents file, which is
     a list of n-tuples.  Each n-tuple will contain:
         package-name description URL
     Examples:
         Tcl-DP  {Distributed programming extension to Tcl} {http://.../dp.tek}

----------
I'm still not happy with the name -- "practcl" is too
many syllables, and doesn't really reflect the point of
the package, and looks bad.  It's a Wish Installer or a
Tcl Installer, so maybe Winst?  Tinst?  WinTin?  WinstTin?
WinsTcl?  Winsical (Wish installer for Tcl)  Genie?
(granter of wishes :-)

In any case, there's a couple of issues we have to cover.
First, the UI should look like WISE, and 


tclPkgInfo global variable
    stores exec_prefix, prefix, tclConfig.sh, spamGlobals

pkgIndex files
    package ifneeded ....
    set elements in tcl_pkgInfo variable
       - or -
    use packages name space

Add [info library]/pkgInfo.tcl to core
    sets the tclPkgInfo array, defines aux procs
init.tcl sources pkgInfo.tcl

Extension .tcl files:
    [info library]/$pkg$ver/
    $env(TCL_LIBRARY_PATH)/$pkg$ver/
    any of tcl_pkgPath
    $tclPkgInfo(prefix)/pkg$ver/
    user selected

Extension .dll (.so) files
    [info library]/$pkg$ver/
    $env(TCL_LIBRARY_PATH)/$pkg$ver/
    any of tcl_pkgPath
    $tclPkgInfo(exec_prefix)/pkg$ver/
    user selected

Extensions to bundles
    .spm file format:
    set installInfo(packages) {...}
    set installInfo($pkg,name) dp
    set installInfo($pkg,version) dp


package install <bundle-file> ?package ...?

In unix:
    install*
        #!tclsh
        package install foo.spm {packages}

--------------
Low priority:
Should modify registry (what?)
    Allows unstaller to run

Very low priority:
    Allow extension writer to add icon
