Add/Edit apps/envs - frontend

[jopache]

blocked: #12 (add/edit apps/envs backend)

Write frontend code to allow adding/editing (possibly moving) an application/environment. For now I will assume it will use the same recursive treenode component that the application started with however the "moving" of a node might get somewhat complex and it might make sense to move to a third party tree view component that already supports drag functionality.