Add support for GemStone 64

[gcotelli]

• Add rowan specs
• Split some packages including Pharo-specific code
• Make TCP command server optional (and only available in Pharo by now)
• Refactor environment variable access to use the facilities in the language platform
• Port the useful parts of CommandLineArguments and CommandLineHandler to GS, and move the other methods to a compatibility package to not break Pharo when loaded.
• Provide a GS64 version of StackTraceTextDumper

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (9c57522) 99.78% compared to head (e168b01) 99.78%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           release-candidate      #51   +/-   ##
==================================================
  Coverage              99.78%   99.78%           
==================================================
  Files                     56       56           
  Lines                   3646     3688   +42     
==================================================
+ Hits                    3638     3680   +42     
  Misses                     8        8           

Files Changed	Coverage Δ
...Commands-Pharo-Tests/TCPCommandServerTest.class.st	100.00% <ø> (ø)
...Launchpad-Commands-Pharo/TCPCommandServer.class.st	100.00% <ø> (ø)
...e/Launchpad-Commands/LaunchpadRootCommand.class.st	100.00% <ø> (ø)
...lications/CurrentApplicationConfiguration.class.st	100.00% <100.00%> (ø)
...unchpad-Applications/LaunchpadApplication.class.st	100.00% <100.00%> (ø)
...hpad-Applications/ReleasedApplicationMode.class.st	100.00% <100.00%> (ø)
...nds-Pharo/LaunchpadTCPCommandServerOption.class.st	100.00% <100.00%> (ø)
...d-Commands-Tests/LaunchpadRootCommandTest.class.st	100.00% <100.00%> (ø)
source/Launchpad-Commands/LaunchpadOption.class.st	100.00% <100.00%> (ø)
...Commands/LaunchpadStartApplicationCommand.class.st	100.00% <100.00%> (ø)
... and 7 more

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