Move plug-in pages

[allejo]

Page: https://wiki.bzflag.org/Plug-ins

What to migrate/rewrite:

• Compilation instructions for different platforms
• Loading plugins for server owners
• List of official plugins or just link to GitHub?

[TheGiraffe3]

MacOS plugin building (this is the only way I could find and make work. If there is an official way we should include that instead, this one is tacky):

• Download BZFlag.
• Download the plugin you wish to compile.
• Using Finder, go into the "Xcode" folder for BZFlag. Right-click on BZFlag.xcodeproj and click "Show Package Contents".
• Go to the .pbxproj file and press Cmd-I. Under "Open With" select "TextEdit".
• Open the file and replace all instances of "SAMPLE_PLUGIN" with the name of the plugin you wish to compile.
• Copy the plugin directory into ../../plugins. Make sure the README and .cpp files have the same name.
• Open Xcode and select the Build Target as the plugin you want to compile.
• Click the Start button. You'll find the compiled plugin in Library/Application\ Support/Xcode/DerivedData/BZFlag-[some sequence of numbers and letters]/Compiled/Debug.