C#: Update qlpath to fix metric queries.

The Metrics folder has a queries.xml file which is required when
building a full distribution, as the Metrics folder gets copied into
odasa-csharp-metrics directory. However, in QL for Eclipse this doesn't
compile because it prevents import lookup at the top level. Modifying
the qlpath file to include the top-level directory on the library path
fixes the problem.

Author: lcartey

csharp/ql/src/.qlpath

@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <ns:qlpath xmlns:ns="https://semmle.com/schemas/qlpath">
-    <librarypath></librarypath>
+    <librarypath>
+        <path>/semmlecode-csharp-queries</path>
+    </librarypath>
     <dbscheme kind="WORKSPACE">semmlecode-csharp-queries/semmlecode.csharp.dbscheme</dbscheme>
-    <defaultImports><defaultImport>csharp</defaultImport></defaultImports>
+    <defaultImports>
+        <defaultImport>csharp</defaultImport>
+    </defaultImports>
 </ns:qlpath>