Some additions to the DB walkthrough (#1309)

cmd/pics/state.go

docs/programmers_guide/changes_0_AccountChanges.png

docs/programmers_guide/changes_0_BlockBodies.png

docs/programmers_guide/changes_0_HeaderNumbers.png

docs/programmers_guide/changes_0_Headers.png

docs/programmers_guide/changes_0_HistoryOfAccounts.png

docs/programmers_guide/changes_0_PlainState.png

docs/programmers_guide/changes_0_Receipts.png

docs/programmers_guide/changes_1_AccountChanges.png

docs/programmers_guide/changes_1_BlockBodies.png

docs/programmers_guide/changes_1_HashedState.png

docs/programmers_guide/changes_1_HeaderNumbers.png

docs/programmers_guide/changes_1_Headers.png

docs/programmers_guide/changes_1_HistoryOfAccounts.png

docs/programmers_guide/changes_1_PlainState.png

docs/programmers_guide/changes_1_Receipts.png

docs/programmers_guide/changes_1_Senders.png

docs/programmers_guide/changes_1_SyncProgress.png

docs/programmers_guide/changes_1_TransactionIndex.png

docs/programmers_guide/changes_1_TransactionSenders.png