Fix a nullref if an unknown unit type is present in the statistics

Found by coverity
RCA AI: fix a bug that kept surrounded units from attacking

In the equation below the line changed, support is a measure of how
many AI units can come and aid the attacking unit.  For a surrounded
unit, support=0, and thus the attack rating (value) was previously
always zero, meaning that the unit never attacked.
This fixes bug #21334:
Add a !null assert

Found by coverity
Add a !null assert

Found by coverity
Add missing braces around a multiline block

Found by coverity
Add missing break

Found by coverity
Add missing break

Found by coverity
Don't increment an iterator if it's past the end

Found by coverity
Don't increment an iterator if it's past the end

Found by coverity
added party full notification sound
changed notification sound to "turn bell" which is better
added game_config::sounds::party_full_sound, defaults to turn bell
and switched multiplayer_connect.cpp to use this sound
changed debugging output message
changed the logic for the bell:
connect engine must report no sides are available and game can start.
updated Japanese translation
fixed number of chars per line for changelogs
Ignore project files for all versions of QtCreator.
Display custom options directly on the configure screen.
Set initial values for custom options.
Make custom sliders and textboxes wider.
A bit more sophisticated layout for custom options.