added missing translation strings (#888)

src/main/resources/messages_ko_KR.properties

@@ -413,6 +413,7 @@ BookToPDF.tags=Book,Comic,Calibre,Convert,manga,amazon,kindle
 ###########################
 #login
 login.title=로그인
+login.header=로그인
 login.signin=로그인
 login.rememberme=로그인 유지
 login.invalid=사용자 이름이나 비밀번호가 틀립니다.
@@ -951,6 +952,7 @@ PDFToCSV.prompt=Choose page to extract table
 PDFToCSV.submit=??
 
 #split-by-size-or-count
+split-by-size-or-count.title=Split PDF by Size or Count
 split-by-size-or-count.header=Split PDF by Size or Count
 split-by-size-or-count.type.label=Select Split Type
 split-by-size-or-count.type.size=By Size