Restructure .gitignore file
gitignore: Restructure existing rules

Organize the rules into groups corresponding to the tools creating
these files.

Use blank lines and comments for clarity.
gitignore: Keep README and COPYING files
gitignore: Additional cmake rules
gitignore: Merge rules from po/**/.gitignore files
Remove unnecessary translation scripts

The new gitignore rules will automatically ignore these.
gitignore: Merge dozens of "Thumbs.db" rules

It suffices to apply the rule once in the root directory.
gitignore: Reduce number of false positives

Especially in utils/umc_dev/ a massive number of files matched ignore
rules. As tracked files can't be ignored, this had no real consequences.
gitignore: Fix order of rules for Makefiles

The exceptions were applied before the generic rule, thus they had
no effect.
gitignore: Block some extensions
gitignore: Merge rules from projectfiles/
gitignore: Include more rules from subdirectories

That is: data/lua/, scons/, and utils/
gitignore: Merge rules from doc/ and data/tools
Remove remove-potcdate.sin from wescamp-import

If we delete the remove-potcdate.sin scripts, we may as well remove the paragraph importing them.
refactor tod_manager::get_illuminated_tod to take map as an arg

Helps to encapsulate, and eliminate unnecessary resources::pointers.
refactor tod_manager::get_illuminated_tod to take unit_map as arg

Improve encapsulation, eventually remove all resources::pointers
from this object.
Don't call preprocess_file() on an empty path if fonts.cfg can't be found

get_wml_location() returns an empty string on failure, and there is
really no point in calling preprocess_file() on that -- it only results
in a confusing error message.

Replaces this sequence often found when Wesnoth can't resolve the path
to its data directory:

  20140612 23:37:05 error filesystem: Trying to open file with empty name.
  20140612 23:37:05 error config: Could not open file
  could not initialize fonts

... with the following one:

  20140612 23:38:52 error font: could not resolve path to fonts.cfg, file not found
  could not initialize fonts

... which should be a little bit more helpful in pointing users in the
right direction in the aforementioned case.
Suggest checking the data dir path when unable to initialize fonts

Not being able to initialize fonts is usually the direct consequence of
a failure to read data/hardwired/fonts.cfg, possibly because the game
data dir was incorrectly set or detected. Thus, it's the ideal point
during early initialization to provide a hint on stderr for players.

I specifically avoided mentioning anything about "installing" the game
so as to not contribute to the common misconception that the game needs
to be installed to run.
refactor tod_manager::set_turn, next_turn, accept game_data arg

This improves encapsulation and almost allows to push resources
out of the tod_manager
Add documentation for warn_early_init_failure()

Because the odds of someone altering the early init sequence in the
future and failing to realize the purpose of this code aren't low
enough. (I really should've included it in the main commit.)