code: Fix incorrect listing of files in subdirectory

Reason: jgit-log produces incorrect logs under the certain conditions.
For the detailed bug report, see
http://dev.eclipse.org/mhonarc/lists/jgit-dev/msg02461.html

Solution: If jgit-log gives incorrect commit while commit traversal,
skip the commit and continue.
config: Set the preferred language to english

Problem: controllers.ImportAppTest fails if the language of the system,
running the test, is not supported by Yobi.

Reason: The default language is English, to which has been set by
renaming conf/messages.en to conf/messages at 7a1ecd9, but the
preferred language is Korean, to which has been set by modifying
application.langs configuration at e2b529b.

Solution: Unify the default and preferred language by setting the
preferred language to English from Korean.
Markdown: Fix javascript warning when code lang of parameter is null
Merge branch 'issue/markdown-code-lang' of insanehong/hive

from pull request 964
Merge branch 'fix/codebrowser-misses-some-files-in-subdir' of npcode/yobi

from pull request 896
Merge branch 'config/prefers-english' of npcode/yobi

from pull request 957