qmljs: added persistent trie

Add a presistent trie to store imports, and provide a better (IMHO)
completion algorithm.
The trie is quite generic and it might be worth while to move it to utils.

Change-Id: I4081346af6215b1ee8ff14bd063c2a021d7c8218
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>

src/libs/qmljs/qmljs-lib.pri

@@ -37,7 +37,8 @@ HEADERS += \
     $$PWD/consolemanagerinterface.h \
     $$PWD/consoleitem.h \
     $$PWD/iscriptevaluator.h \
-    $$PWD/qmljssimplereader.h
+    $$PWD/qmljssimplereader.h \
+    $$PWD/persistenttrie.h
 
 SOURCES += \
     $$PWD/qmljsbind.cpp \
@@ -65,7 +66,8 @@ SOURCES += \
     $$PWD/jsoncheck.cpp \
     $$PWD/consolemanagerinterface.cpp \
     $$PWD/consoleitem.cpp \
-    $$PWD/qmljssimplereader.cpp
+    $$PWD/qmljssimplereader.cpp \
+    $$PWD/persistenttrie.cpp
 
 RESOURCES += \
     $$PWD/qmljs.qrc