[FAB-8182] Remove old configtxgen doc

The new command doc layout makes the old configtxgen document
superfluous.  However, there was still some content in the old doc that
was useful to preserve, and has not been moved to the command doc.

This CR also updates the referenced profiles to be the more recent V1_1
capability profiles, as was suggested in a review of the doc, but
deferred for a later CR.

Change-Id: I77a9e8e56c8fbf19e27b040279a4b74150f17ffb
Signed-off-by: Jason Yellick <jyellick@us.ibm.com>

docs/source/commands/configtxgen.md

@@ -41,19 +41,19 @@ Usage of configtxgen:
 ### Output a genesis block
 
 Write a genesis block to `genesis_block.pb` for channel `orderer-system-channel`
-for profile `SampleSingleMSPSolo`.
+for profile `SampleSingleMSPSoloV1_1`.
 
 ```
-configtxgen -outputBlock genesis_block.pb -profile SampleSingleMSPSolo -channelID orderer-system-channel
+configtxgen -outputBlock genesis_block.pb -profile SampleSingleMSPSoloV1_1 -channelID orderer-system-channel
 ```
 
 ### Output a channel creation tx
 
 Write a channel creation transaction to `create_chan_tx.pb` for profile
-`SampleSingleMSPChannel`.
+`SampleSingleMSPChannelV1_1`.
 
 ```
-configtxgen -outputCreateChannelTx create_chan_tx.pb -profile SampleSingleMSPChannel -channelID application-channel-1
+configtxgen -outputCreateChannelTx create_chan_tx.pb -profile SampleSingleMSPChannelV1_1 -channelID application-channel-1
 ```
 
 ### Inspect a genesis block
@@ -87,9 +87,40 @@ configtxgen -printOrg Org1
 ### Output anchor peer tx
 
 Output a configuration update transaction to `anchor_peer_tx.pb` which sets the
-anchor peers for organization Org1 as defined in profile SampleSingleMSPChannel
-based on `configtx.yaml`.
+anchor peers for organization Org1 as defined in profile
+SampleSingleMSPChannelV1_1 based on `configtx.yaml`.
 
 ```
-configtxgen -outputAnchorPeersUpdate anchor_peer_tx.pb -profile SampleSingleMSPChannel -asOrg Org1
+configtxgen -outputAnchorPeersUpdate anchor_peer_tx.pb -profile SampleSingleMSPChannelV1_1 -asOrg Org1
 ```
+
+## Configuration
+
+The `configtxgen` tool's output is largely controlled by the content of
+`configtx.yaml`.  This file is searched for at `FABRIC_CFG_PATH` and must be
+present for `configtxgen` to operate.
+
+This configuration file may be edited, or, individual properties may be
+overridden by setting environment variables, such as
+`CONFIGTX_ORDERER_ORDERERTYPE=kafka`.
+
+For many `configtxgen` operations, a profile name must be supplied.  Profiles
+are a way to express multiple similar configurations in a single file.  For
+instance, one profile might define a channel with 3 orgs, and another might
+define one with 4 orgs.  To accomplish this without the length of the file
+becoming burdensome, `configtx.yaml` depends on the standard YAML feature of
+anchors and references.  Base parts of the configuration are tagged with an
+anchor like `&OrdererDefaults` and then merged into a profile with a reference
+like `<<: *OrdererDefaults`.  Note, when `configtxgen` is operating under a
+profile, environment variable overrides do not need to include the profile
+prefix and may be referenced relative to the root element of the profile.  For
+instance, do not specify
+`CONFIGTX_PROFILE_SAMPLEINSECURESOLO_ORDERER_ORDERERTYPE`,
+instead simply omit the profile specifics and use the `CONFIGTX` prefix
+followed by the elements relative to the profile name such as
+`CONFIGTX_ORDERER_ORDERERTYPE`.
+
+Refer to the sample `configtx.yaml` shipped with Fabric for all possible
+configuration options.  You may find this file in the `config` directory of
+the release artifacts tar, or you may find it under the `sampleconfig` folder
+if you are building from source.