Useful and consistent tool tips

[soininen]

This issue is about tool tips associated with user interface actions such as tool bar buttons, text fields, etc.

Many actions do not have tool tips at all or the tool tip is just the action's name. In some cases (like 'undo') this should suffice but many actions should have a more explanatory tool tips.

Actions where the action's name suffices as tool tip unless the action does something surprising:

• new
• open
• redo
• save
• save as
• undo
• other actions where the tool tip feels redundant

To make tool tips consistent, we should follow some guidelines

• The verb should be in simple present: "Show commit viewer", not "Shows commit viewer".
• Tool tips are usually not full sentences so there is no need to add a dot to the end
• Keyboards shortcut, if any, should be included in the tool tip by add_keyboard_shortcut_to_tool_tip(). For actions that are in the .ui files, a call to add_keyboard_shortcuts_to_action_tool_tips() in the widget's __init__() will do the job.

Check that tool tips follow the above guidelines and fix odd cases:

• In Toolbox main window
• In Toolbox dialogs
• In Database editor
• In Spine items