[lib] make microcode optional for schema and remove from csv_importer

lib/refrepo/csv_importer.rb

@@ -118,7 +118,6 @@ nodes:
       cache_l2: 8 # Fake cache, will be replaced by g5k-checks
       cache_l3: 8 # Fake cache, will be replaced by g5k-checks
       instruction_set: x86-64 # Common instruction set, will be replaced by g5k-checks
-      microcode: "0xd000001" # Fake microcode, will be replaced by g5k-checks
       ht_capable: true # Default ht capable value, will be replaced by g5k-checks 
     main_memory:
       ram_size: 8 # Fake ram size, will be replaced by g5k-checks

lib/refrepo/valid/input/schemas/schema-node.yaml

@@ -102,7 +102,7 @@ processor:
   cache_l3: integer
   clock_speed: integer
   instruction_set: string
-  microcode: string
+  microcode: optional_string
   model: string
   other_description: string
   vendor: string