Skip nodes functionality for Package and Network modules

Added to main entrypoint
- Skip nodes using simple argument with '*' as a trailing wildcard
- Skip nodes using file list

Usability improovement
- Node list preview in status line
- Node stats alignment in net report

Minor fixes:
- Python version detection (3.5+)
- Node counter for each status
- Proper node skip handling

Change-Id: I086ef501bc06f0e739df25349257f1c63a2e2fcf
Related-PROD: PROD-35009
diff --git a/cfg_checker/modules/network/mapper.py b/cfg_checker/modules/network/mapper.py
index 483c11f..51f52bb 100644
--- a/cfg_checker/modules/network/mapper.py
+++ b/cfg_checker/modules/network/mapper.py
@@ -31,12 +31,21 @@
     CONFIG = "config"
     RUNTIME = "runtime"
 
-    def __init__(self, errors_class=None):
+    def __init__(
+        self,
+        errors_class=None,
+        skip_list=None,
+        skip_list_file=None
+    ):
         logger_cli.info("# Initializing mapper")
         # init networks and nodes
         self.networks = {}
-        self.nodes = salt_master.get_nodes()
+        self.nodes = salt_master.get_nodes(
+            skip_list=skip_list,
+            skip_list_file=skip_list_file
+        )
         self.cluster = salt_master.get_info()
+        self.domain = salt_master.domain
         # init and pre-populate interfaces
         self.interfaces = {k: {} for k in self.nodes}
         # Init errors class