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/common/const.py b/cfg_checker/common/const.py
index 685c79a..3b17099 100644
--- a/cfg_checker/common/const.py
+++ b/cfg_checker/common/const.py
@@ -8,6 +8,7 @@
 _cnt = itertools.count()
 NODE_DOWN = next(_cnt)
 NODE_UP = next(_cnt)
+NODE_SKIP = next(_cnt)
 
 # version const order is important!
 # biggest get shown in report top row
@@ -42,12 +43,13 @@
     VERSION_DOWN: "downgraded",
     VERSION_WARN: "warning",
     VERSION_ERR: "error",
-    VERSION_NA: "no status"
+    VERSION_NA: "nostatus"
 }
 
 node_status = {
     NODE_UP: "up",
-    NODE_DOWN: "down"
+    NODE_DOWN: "down",
+    NODE_SKIP: "skip"
 }
 
 uknown_code = "unk"