Update doc for init-frz-model (#1107)

* enable init-frz-model support for the original model within the dp train interface

* add init_variables method for ABC

* add doc for embedding_net method

* update doc for init-frz-model

Author: denghuilu

doc/train/training-advanced.md

@@ -109,7 +109,7 @@ optional arguments:
 
 **`--restart model.ckpt`**, continues the training from the checkpoint `model.ckpt`.
 
-**`--init-frz-model frozen_model.pb`**, initializes the training with an existing model that is stored in `frozen_model.pb`. Note that the `init-frz-model` command only supports the compressed model currently!
+**`--init-frz-model frozen_model.pb`**, initializes the training with an existing model that is stored in `frozen_model.pb`.
 
 On some resources limited machines, one may want to control the number of threads used by DeePMD-kit. This is achieved by three environmental variables: `OMP_NUM_THREADS`, `TF_INTRA_OP_PARALLELISM_THREADS` and `TF_INTER_OP_PARALLELISM_THREADS`. `OMP_NUM_THREADS` controls the multithreading of DeePMD-kit implemented operations. `TF_INTRA_OP_PARALLELISM_THREADS` and `TF_INTER_OP_PARALLELISM_THREADS` controls `intra_op_parallelism_threads` and `inter_op_parallelism_threads`, which are  Tensorflow configurations for multithreading. An explanation is found [here](https://stackoverflow.com/questions/41233635/meaning-of-inter-op-parallelism-threads-and-intra-op-parallelism-threads).