And a minor visual tweak to the line numbering

Stealing code from MeteoIO, the copyright notice now shows the user name
and domain name (if available)

Noteworthy: Removed fixed shortcut in doc because it is OS-dependent.

A small inconsistency has been fixed in Number.cc (now using the
background color instead of hard-coded white). The PATH is now expanded
to include the directory where inishell is (this will be convenient for
packaging with small applications). The NSIS templates for Windows have
been copied, but there is still work to do before it can be useful.

As well as a minot tweak in the project file

More integration of keyboard shortcuts: Add menu for 'refresh applications' so that the user can find the native shortcut for it. In the welcome text, use the nativ shortcut for the help hint.

Don't mention key shortcuts in the help file anymore.

Move one more function to 'os' - now only small tweaks are left scattered in the code and the core OS functionality is bundled.

(Because the rest of INIshell is very clean concerning OS-specific code, so it's nice to collect it)