Added fully qualified dbc, node, and msg searching

...to graphing window and signal viewer so complex systems with message
name duplication (eg "Status") works well.  DBCHandler class has a new
function to find a msg by fully qualified node name...Utility class defines
the qualified name seperator, right now it is :: and is used thusly
filenameNoExtension::nodeName for display in the node dropdown (because
nodes can be common between dbc files).  To get the message from the
system you use the findMessage function in dbchandler and pass the
msgName and the fully qualified node name.  This is about as unique as we
can get, second only to message ID.

Added node comboBox to graph signal editor for easier data filtering
(took the same implementation that was in signal viewer, and tuned up
both of them)

dbc/dbchandler.h

@@ -82,6 +82,7 @@ public:
     bool loadFile(QString);
     QString getFullFilename();
     QString getFilename();
+    QString getFilenameNoExt();
     QString getPath();
     int getAssocBus();
     void setAssocBus(int bus);
@@ -121,6 +122,8 @@ public:
     void swapFiles(int pos1, int pos2);
     DBC_MESSAGE* findMessage(const CANFrame &frame);
     DBC_MESSAGE* findMessage(const QString msgName);
+    DBC_MESSAGE* findMessage(const QString msgName, const QString fullyQualifiedNodeName);
+    DBC_MESSAGE* findMessage(const QString msgName, const QString nodeName, const QString fileNameNoExt);
     DBC_MESSAGE* findMessage(uint32_t id);
     DBC_MESSAGE* findMessageForFilter(uint32_t id, MatchingCriteria_t * matchingCriteria);
     int getFileCount();