PapiExecutor always verifies

Do not support returning unverified replies anymore.
Basically, ".get_replies().verify_replies()" is now just ".get_replies()".
This allows fairly large simplifications both at call sites
and in PapiExecutor.py

+ Rename get_dumps to get_details.
+ Introduce get_reply and get_sw_if_index.
+ Rename variables holding get_*() value,
  + e.g. get_stats() value is stored to variable named "stats".
  + Rename "item" of subsequent loop to hint the type instead.
  + Rename "details" function argument to "verbose".
+ Process reply details in place, instead of building new list.
  - Except hybrid blocks which can return both list or single item.
  - Except human readable text building blocks.
+ Rename most similar names to sw_if_index.
  - Except "vpp_sw_index" and some function names.
+ Use single run_cli_cmd from PapiExecutor.
+ Do not chain methods over multiple lines.
  + Small space gain is not worth readability loss.
+ Include minor code and docstrings improvement.
+ Add some TODOs.

Change-Id: Ib2110a3d2101a74d5837baab3a58dc46aafc6ce3
Signed-off-by: Vratko Polak <vrpolak@cisco.com>