use CmakeLists scope to generate te XML file

- the only difference really is, that scope (the configuration.cmake) is already passed
  to px_process_params via the argument --scope. The Paths in --scope are evaluated w.r.t
  the path to src provided via the -s /--src-path argument.
- if no --scope is proveided. the Old scheme by simply walking the full --src-path directory
  is applied

Tools/px4params/cmakeparser.py

@@ -0,0 +1,37 @@
+import re
+import codecs
+import sys
+
+class CMakeParser(object):
+    """
+    Parses provided data and stores all found paths in scope.
+    """
+    re_split_lines = re.compile(r'[\r\n]+')
+    re_comment = re.compile(r'^\#')
+    re_start = re.compile(r'set\s*\(\s*config_module_list')
+    re_end = re.compile(r'\)\s*')
+
+    def Parse(self, scope, contents):
+        """
+        Incrementally parse cmake file contents and append all found path scope
+        to scope.
+        """
+        # This code is essentially a comment-parsing grammar. "state"
+        # represents parser state. It contains human-readable state
+        # names.
+        state = None
+        for line in self.re_split_lines.split(contents):
+            line = line.strip()
+            # Ignore empty lines
+            if line == "":
+                continue
+            if self.re_comment.match(line):
+                continue
+            elif self.re_start.match(line):
+                state = "gather"
+                continue
+            elif state is not None and state == "gather":
+                if self.re_end.match(line):
+                    return True
+                scope.Add(line)
+        return False