Remember package refactor17388

[AlexisCnockaert]

Fixes: #17388 I created a class variable to remember lastselected package, the next time its searched by default

Here it is remembered :

[Ducasse]

Pay attention Instance variable names must start with a lowercase letter: {ClySystemBrowserContext class}

[Ducasse]

Alexis you should use a class variable (sharedVariables: and not an instance variables of the metaclass. Please read the Pharo by example chapter so that you get it right because knowing the difference it important. There is also a video on the pharo mooc.