DB-Layer fixes/enhancements (sonic-net#26)

Added additional DBs
NoDelete option used (Set|Mod)Entry
MultiDB changes
GetKeysByPattern(), Publish(), RunScript()
DeleteKeys() bug fix

Author: a-barboza

tools/test/database_config.json

@@ -0,0 +1,56 @@
+{
+    "INSTANCES": {
+        "redis":{
+            "hostname" : "127.0.0.1",
+            "port" : 6379
+        }
+    },
+    "DATABASES" : {
+        "APPL_DB" : {
+            "id" : 0,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "ASIC_DB" : {
+            "id" : 1,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "COUNTERS_DB" : {
+            "id" : 2,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "LOGLEVEL_DB" : {
+            "id" : 3,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "CONFIG_DB" : {
+            "id" : 4,
+            "separator": "|",
+            "instance" : "redis"
+        },
+        "PFC_WD_DB" : {
+            "id" : 5,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "FLEX_COUNTER_DB" : {
+            "id" : 5,
+            "separator": ":",
+            "instance" : "redis"
+        },
+        "STATE_DB" : {
+            "id" : 6,
+            "separator": "|",
+            "instance" : "redis"
+        },
+        "SNMP_OVERLAY_DB" : {
+            "id" : 7,
+            "separator": "|",
+            "instance" : "redis"
+        }
+    },
+    "VERSION" : "1.0"
+}