Memory Migration Failure for new deploys

[OverlordQ]

Issue summary

Fresh Spawn cannot init properly

Description of issue:

The initial migration fails in 0.5.3->0.6.x part 5 due to the deletes on Memory.stats.persistent.terminalNetwork.transfers because Memory.stats.persistent not existing. If you wrap that in a try block to have it continue it fails in onGlobalReset at Memory.stats.persistent.lastGlobalReset = Game.time; because Memory.stats.persistent also doesn't exist.

Steps to reproduce:

1. Clear all Memory
2. Deploy dev branch

Suggested fix (optional):

index 2400702..cbb766f 100644
--- a/src/memory/Memory.ts
+++ b/src/memory/Memory.ts
@@ -183,7 +183,7 @@ export class Mem {
                        spawns            : {},
                        pathing           : {distances: {}},
                        constructionSites : {},
-                       stats             : {},
+                       stats             : {persistent: {}},
                        playerCreepTracker: {},
                        settings          : {
                                signature             : DEFAULT_OVERMIND_SIGNATURE,```

### Other information:

‣ Version: Overmind v0.5.2
‣ Checksum: 0x0
‣ Assimilated: No (clearance code: null) [WIP]
‣ Operating mode: automatic
‣ Commit: c1cccf3

[OverlordQ]

This seems to be same underlying issue as PR #161