fixup [filter_vision] tags

This is the master version of PR #237, with unit tests.
add [has_ally],[has_enemy] tags for standard side filter

Unlike [allied_with] and [enemy_of], these will match if only if
there is *any* ally or enemy matching the filter. The other versions
of the tag match only if all sides matching the filter are
allied / opposed.

This commit also adds a unit test that checks that it works as
expected.
 This patch adds a feature mentioned in http://wiki.wesnoth.org/EasyCoding,
namely the first one in "Engine related features". To implement this feature, I added the command field in the configuration for the context menu.

This comes as an alternative to https://github.com/wesnoth/wesnoth/pull/246
update changelog
Merge branch 'has_ally_master'

Conflicts:
	wml_test_schedule
update changelog
Merge branch 'master' of git://github.com/wesnoth/wesnoth

Conflicts:
	changelog
updated French translation
remove executable flag from french manual images
updated Vietnamese translation
fixed Vietnamese manpages
remove outcommented code
Fix a Doxygen comment error.

The issue was found by CLang.
Fix a Doxygen comment error.

The issue was found by CLang.
Remove a useless semicolon.
Remove a useless semicolon.
Improve a horrible enumerate conversion.

Two improvements were made.
- By adding a default in a case in a switch statement the compiler can
  no longer warn when a member of the enumerate is not handled.
- The exception thrown had no message, so added a message. This also
  required to change the type of the exception to a more appropriate
  type.
Fix a comment typo.
Strip trailing whitespace.
Integrate create_engine into sp campaign selection

After campaign selection, the mp codepath is followed starting with
enter_configure_mode().
Code for sorting and marking completed campaigns, as well as for difficulty selection, has been moved to create_engine.
Also, [scenario] tags are now converted to [multiplayer] for sp as in mp.

Conflicts:
	src/game_controller.cpp
	src/multiplayer.cpp