Hand out a default for Dialog.return_events

Was probably intended this way.
Fix issues with Dialog conversion of RenameDialog

Hopefully addresses what @squiddy pointed out for 50bff9e4.
Drop a blank line

Made sense back when this was part of a thirty-line __init__.
Drop a line of cleanup code that's no longer required

We load the widget (with empty text field) from scratch whenever it is
displayed, so clearing the text right before dismissing the entire
widget doesn't make much sense here.
Fix rename gui tests

Converting to Dialog apparently made them need handlers now.
Update release tools, added script to create a linux tarball

Conflicts:
	development/create_release.sh
Fix link to (old) wiki

Will be migrated rather soon in any case, but as long as there are no
concrete plans, this might work better.
Revert "Hand out a default for Dialog.return_events"

Totally not intended this way, apparently. Broke lots of confirmation
popups. Triggered #2029 on the way. Sorry for this!
This reverts commit 162fa42bf0219137610455e23dfebfa87474afb5.
Fixes #2029
More helpful headline for map saving error popup
Commit from Unknown Horizons Translation Server by user Chris Oelmueller.: 209 of 369 strings translated (14 fuzzy).
Replace dummy of message_widget with real instance.

This is done because message_widget was needed to show messages in the editor. A logbook dummy is created in order for message_widget to work.
Modify save_map to return whether it was succesful
Clean up error popup on failed quicksave

Drop unicode in gettext-wrapped strings, use format()
Modify editor quicksave and autosave to handle failure
Add showprice keyword arg to ImageStatusFillButton init
Add information about price in tooltip in Select Resources widget
Add support for different buy and sell prices; show price as float
Whitespace
Add ThePawnBreak to list of contributors
Drop a few assumptions about amount of music tracks

In particular we would crash if there were three or fewer tracks
available as a whole and if the menu music tried to refresh playlist
while no menu_music existed at that point.
Now restricts the deque length such that it can hold at most one track
less than the amount of tracks available.