More usability and polish updates

I have been working of a development branch but now we are stable I am merging to stable. Here are some of the new features to look forward to:

• Tooltips on most buttons. Should help explain the interface to newcomers.

• New scoring system. Your score is now the worst test result and you need a score of more than 0 to pass. Makes accuracy less important than functionality.

• Custom elements. You can customize a sub-design to suit its use without having to change your original.

• Copy and paste of selected elements. Allows you to copy parts or even entire designs between levels.

• Element reflections. You can flip elements so their ports are have more convenient positions.

• Selection rotate. You can rotate groups of elements to reposition them in your design.

• Confirmation when overwriting or deleting saves.

• MacOS 10.14 and Debian stable compatibility. I moved the compile jobs to older VMs so we maintain compatibility for older OSs.

• Score autosubmit to server. Will keep your designs updated on the server to your latest best version.

• Hints! You can get a hint if you are stuck on a level. Less fun, but it can get you over a mental block.

• Even more levels! We are up to 28 now.

Enjoy!