OK, a bunch of changes and meta-fixes

[neroden]

James, you've probably already noticed these by looking at my ncn-devel branch...

- Most important change: overrides.
pak_overrides_savegame_settings will allow you to blow away old savegame settings and load your savegame with the newest version of the pak.  I have this on permanently.  (It does not apply when operating in network mode as a client, for obvious reasons.)

- There was a very nasty bug where the "in-transit" count for factories receiving goods sometimes got incremented but not decremented, when goods were thrown away for waiting too long.  Worse, the bad values persisted across saves.  Worse than that, a pak setting would cause the factory to refuse to demand more goods because it thought so many were in transit.  In addition to fixing what appeared to be the root cause of the bug, I made sure the situation is cleaned up on reloading.  And I adjusted the pak128.britain.experimental setting because it was preventing steady supply to factories across long ship routes.

- Route searches were starting out with uninitialized axle limits and weight limits; the possiblility of random bad data in these has been eliminated.
- A number of subtle problems with bridge pillars showing up, or not showing up, were fixed.

- Cities do not adopt elevated and underground roads within their limits.  This was too abuse-prone.

- City building placement is substantially "prettier".  (Third round of prettier...)  Buildings will prefer to face a flat road; if they can't find one they will prefer to face a road.  Buildings will align on the same level as the square they are facing.  As an aesthetic choice, if the road the building faces isn't flat, the building will align with the lower level; I find that this looks better *most* of the time, due to the presence of "zero setback" building artwork, which looks really odd facing forward on the top of a cliff.

Very little of this applies when a building is constructed in a way which is not orthogonally adjacent to a road, so I removed those options from my versino of the pak128.britain.experimental cityrules.  I realize the UK does have houses which don't face on a road, but they end up looking kind of ugly in the game.

- I finally got the livery names list loading right (I'd been having recurring problems with either empty lists or duplicated entiries)
- I managed to fix the bug which was putting absolute pak names into save files.
- Roadbuilding by cities and adoption of player roads by cities follows a coherent set of rules now.  They may not be the greatest rules but at least the behavior is consistent rather than bizarre and unpredictable.
- Various minor fixes to uninitialized variables, etc.

[jamespetts]

Thank you very much for this - most helpful.

One very odd bug that the ncn-devel branch seems to have introduced (tested on my "devel-new" branch, and confirmed not present on the 11.x branch) - on my Windows built at least, when loading a pakset from the pakset selector window, the game will hang until the mouse is moved or a key is pressed rather than loading the pakset immediately. I have not tested this in the Linux server build, but, with no direct user interaction, this could cause an intractable hang if the problem reproduces there.