Merge pull request #38 from l/translation_ja

core: update Japanese translations
doc: update Japanese auto-generated files
README.asciidoc: fix links.
README.asciidoc: add anchors to links.
Merge pull request #39 from Mkaysi/links

README.asciidoc: fix links.
doc: update the contribute chapter in developer's guide
core: update German translations
doc: update German documentation
doc: update German faq
doc: update German documentation
doc: update German auto-generated files
doc: add bare display in questions about copy/paste and click on long URLs (FAQ)
irc: fix notify message: "joined" -> "connected"
exec: add options -nf and -cl/-nocl in command /exec

-nf: create a new buffer with free content
-cl: clear new buffer
-nocl: append in new buffer
core: add buffer property "clear"
exec: allow clear of new buffers with /buffer clear
core: update ChangeLog
core: save/restore buffer property "day_change" on /upgrade
core: save/restore buffer property "clear" on /upgrade
core: skip and ignore color attributes before special names like "reset" in gui_color_get_custom