zh_TW.po: fix translation of 'previous' term

Previously this term is translated as "previous one", however it
actually applies to all previous versions.  This commit corrects the
translation and also applies to other same-term-but-different-tranlation
strings for unification.

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>

Conflicts:
	po/zh_TW.po
zh_TW.po: fix wrong punctuation

The correct punctuation for 'period' is '。' in zh_TW locale.

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
zh_TW.po: update translation with wrong format specifier, fix #284

commit ec1d3b6d introduces translation with wrong format specifier.
This commit fixes those strings.

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
zh_TW.po: update translation of "Help"

Currently, the menu named "Help" is directly translated as "幫助"(may read
as verb/noun in Chinese).  I "patched" it to "尋求幫助(Seeking for help)"
hoping it to be more sensible for users who are really need to find some
more help on using git-cola.

This "patch" is indeed "this particular translator's own preference and
convention" rather than "convention of general zh_TW localization
community", so ignore it if you want to keep safe :-).

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Merge pull request #291 from Vdragon/translation_zh_TW

zh_TW translation update

Signed-off-by: David Aguilar <davvid@gmail.com>