Add display_messages() function to Logbook and call it on loading the game.

This fixes the problem of messages being displayed only after the logbook.hide() is called.
updated preview
Merge pull request #2249 from Zappaman/editor

Fix #2016. Update editor preview
Refactor code to resolve #2227 and #2188
Only use compatiblility code for correct fife

version.
Translated using Weblate (Catalan)

Currently translated at 65.9% (550 of 834 strings)
Remove accidently commited file.
Solve "None Resource" bug #2251

I am not sure whether it's necessary to check for the existance of children.
Merge pull request #2241 from pinkfloyda/tooltip_whitelist

Refactor code to resolve #2227 and #2188
refactoring – merge the two ifs

Before, there was one if clause for creating the button variable and another one for capturing the mouse click and assigning a "name". These two ifs have been merged, as the "if" and "else" match identical cases.
Some refactoring in the editor code to make it more understandable

Still a long way to go
capture Container instead of ImageButton

For this it was necessary to add:  event_name="mouseClicked"
Merge pull request #2252 from myrdd/patch-1

Fixes #2251
Whitespace
Update AUTHORS
Translated using Weblate (Czech)

Currently translated at 100.0% (27 of 27 strings)
Translated using Weblate (Catalan)

Currently translated at 73.9% (617 of 834 strings)
Translated using Weblate (Czech)

Currently translated at 100.0% (22 of 22 strings)
Translated using Weblate (Czech)

Currently translated at 100.0% (191 of 191 strings)
Add new key actions for zooming: PgUp / PgDn

As all hotkeys, this can be reconfigured through the hotkey dialog or by
manually editing the settings file.

Closes #2265 (Zoom In/Out shortcut).