- in Properties Tool added more information's regarding the Excellon tools, about travelled distance and job time; fixed issues when doing Properties on the CNCjob objects

- TODO: I need to solve the mess in units conversion: it's too convoluted

FlatCAMObj.py

@@ -5830,7 +5830,7 @@ class FlatCAMCNCjob(FlatCAMObj, CNCjob):
             It is populated in the FlatCAMGeometry.mtool_gen_cncjob()
             BEWARE: I rely on the ordered nature of the Python 3.7 dictionary. Things might change ...
         '''
-        self.cnc_tools = {}
+        self.cnc_tools = dict()
 
         '''
            This is a dict of dictionaries. Each dict is associated with a tool present in the file. The key is the 
@@ -5848,10 +5848,10 @@ class FlatCAMCNCjob(FlatCAMObj, CNCjob):
                           ...
               }
            It is populated in the FlatCAMExcellon.on_create_cncjob_click() but actually 
-           it's done in camlib.Excellon.generate_from_excellon_by_tool()
+           it's done in camlib.CNCJob.generate_from_excellon_by_tool()
            BEWARE: I rely on the ordered nature of the Python 3.7 dictionary. Things might change ...
        '''
-        self.exc_cnc_tools = {}
+        self.exc_cnc_tools = dict()
 
         # flag to store if the CNCJob is part of a special group of CNCJob objects that can't be processed by the
         # default engine of FlatCAM. They generated by some of tools and are special cases of CNCJob objects.