Log messages routed to stdout/stderr as appropriate.

This also uses a dedicated logger instead of passing everything to the
root logger. `overviewer_core` still needs to be updated to reflect
this.

Additionally, `logger.configure` has been simplified.
Using a dedicated logger inside overviewer_core.
docstring for InverseLevelFilter added.
Removed second logger.

The root logger for "overviewer" is now named "`overviewer_core`".
Fixed log format reconfiguration regression.

Commit c991135 introduced a regression where it was no longer possible
to re-configure the loggers once they had been set up. This is now
fixed.
Fixed a crash when redirecting stdout.
findGitVersion() ignores non-versiony tags
fixed new version incantation to work on windows
fixed hiding JSObserver info box when unused
Merge branch 'master' of git://github.com/overviewer/Minecraft-Overviewer
Added clarification on 'northdirection' that it has to do with viewpoint angle
Fixed the way texture.py searched for foliage, grass and chests textures.
This is a "quick-and-dirty fix", you may improve it as I'm novice in Python.
Default files in data/textures have been renamed to reflect changes in new 1.6 texture packs (aka resource packs)
Use https to load external JS

This fixes an annoying problem where browsers generally ignore http javascript on https html
Use https instead of http for icons
Fixed a typo ('leve' -> 'level').
Merge pull request #979 from PotcFdk/master

Fixed a typo ('leve' -> 'level').
It helps if we print the error message
Add explanation about HTTPS
Merge pull request #980 from tswsl1989/https-explanation

Add explanation about HTTPS
Merge pull request #981 from tswsl1989/pngit

It helps if we print the error message