[#41] netmap: Add well-known EC-related network settings

Because big number of chunks can lead to excessive CPU/RAM usage, we
restrict EC policies via network settings.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

netmap/types.proto

@@ -289,6 +289,12 @@ message NetworkConfig {
   // - **WithdrawFee** \
   //   Fee paid for withdrawal of funds paid by the account owner.
   //   Value: little-endian integer. Default: 0.
+  // - **MaxECDataCount** \
+  //   Maximum number of data shards for EC placement policy.
+  //   Value: little-endian integer. Default: 0.
+  // - **MaxECParityCount** \
+  //   Maximum number of parity shards for EC placement policy.
+  //   Value: little-endian integer. Default: 0.
   message Parameter {
     // Parameter key. UTF-8 encoded string
     bytes key = 1 [ json_name = "key" ];