Scientific and Categorized modes disconnect the "currentChanged" signal.
Reconnected the signals after configuring Scientific or Categorized notation.

Used "UniqueConnection" to avoid signal's triggering the same slot multiple times unintentionally.
Creating Cateory tree items as TopTreeItem causes them to be treated like "Settings" or "Data Objects".
When the current tree item is changed (by mouse click or keyboard arrow) they are checked for their type, which disables the buttons to send/receive.
Merge remote-tracking branch 'origin/glenneaux/OP-1004_GCS_UAVObjectBrowser_ScientificNotation_breaks_buttons' into corvuscorax/OP-947_stateestimator-module2
Merge remote-tracking branch 'origin/glenneaux/OP-1027_GCS_UAVObjectBrowser_CategoryTreeItem_ButtonsNotDisabled' into corvuscorax/OP-947_stateestimator-module2