Improve the Keyboard tab and the KeyBindings editor

Summary:

• Change updateKeyBindingsList() to select the last edited keybindings scheme after closing the editor dialog
• Add a tooltip showing the path of each keybinding scheme, this should lessen the confusion when the scheme description and the file name of the .keytab file are different
• Add a button to the Keyboard tab to reset a scheme to its default values, this is only applicable for schemes that exist in both system-wide and user specific locations
• Move a lot of the construction of the keybinding editor widgets from EditProfileDialog to KeyBindingEditor
• Change the wording from "key bindings list" to "key bindings scheme" to differentiate between a keyboard translator "scheme" and the key bindings "list" on the Keyboard tab

KeyBindingEditor:

• Make the KeyBindingEditor a QDialog and set Qt::WA_DeleteOnClose
• Disallow saving a scheme with an empty description
• Add a QLineEdit to show only the rows that have strings matching the text entered in the line edit box
• Reimplement sizeHint() to make the dialog slightly smaller than the Edit Profile dialog, for better visibility of the entries

KeyboardTranslatorManager:

• Make findTranslatorPath() const and public
• Make allTranslators() return type const

Test Plan:

• Editing a key bindings scheme works and closing the dialog selects the edited scheme
• Creating a new scheme works as before
• "Defaults" button works for system-wide schemes if they were previously edited and saved under the user's home dir
• Remove button is only enabled for schemes saved in a dir writable for the user

Reviewers: Konsole, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: konsole-devel, Konsole

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D12981