[glass] Add NetworkTables view entry order setting

[rmheuer]

This adds a setting to the NetworkTables window to group entries and subtables together, similar to how many IDEs organize the project file tree. For me, organizing the entries this way makes it easier to find what I'm looking for, and I think it likely would for other people as well.

This adds 3 modes:

• Combined (default): Same behavior as previously, with all entries and subtables together in alphabetical order.
  
• Entries First: All entries are placed above subtables in the tree view
  
• Subtables First: All subtables are placed above entries in the tree view