Replaced the "make ts" target with a simple shell script

The invocation of lupdate is so trivial that it doesn't really make
sense to set it up through qmake.

Author: bjorn

dist/update-translations.sh

@@ -0,0 +1,3 @@
+# Updates the .ts files based on the strings found in the source code
+# Meant to be run from repository root
+lupdate -locations relative -no-obsolete src -ts translations/*.ts

translations/translations.pro

@@ -61,13 +61,9 @@ OBJECTS_DIR =
 win32:CONFIG -= embed_manifest_exe
 
 TRANSLATIONS = $$prependAppend(LANGUAGES, $$PWD/tiled_, .ts)
-LUPDATE = $$fixSlashes($$[QT_INSTALL_BINS]/lupdate) -locations relative -no-obsolete
 LRELEASE = $$QMAKE_LRELEASE
 isEmpty(LRELEASE):LRELEASE = $$fixSlashes($$[QT_INSTALL_BINS]/lrelease)
 
-ts.commands = cd $$PWD/.. && $$LUPDATE src -ts $$TRANSLATIONS
-QMAKE_EXTRA_TARGETS += ts
-
 win32 {
     TARGET_DIR = .
 } else:macx {