Add the ability to group remote connections in the application tree

Interface improvement - application tree window

• add the ability to create/delete/change application groups
• add the ability to create nested groups
• add the ability to transfer added remote connections between groups
• add a search string in the remote connection tree

Problem: Navigation is difficult after adding a large number of remote connections

Example implementation: Liberica Mission Control

Start with the application tree window and inspect how the existing remote connection tree is represented and edited. Compare its navigation with the Liberica Mission Control example and clarify the expected behavior for groups, nested groups, moving connections, and search. Done means these operations work together and make large remote-connection lists easier to navigate.