sql: tarantoolctl "enter" with set language

This patch allow to use option "--language" with
"tarantoolctl enter" command. Also default value
for language were added in default configuration
file. Language is either SQL or Lua.

Closes #2385.

@TarantoolBot document
Title: Language selection for tarantoolctl
"enter".
User can select either Lua or SQL when he uses tarantoolctl
 "enter" command. It can be done using "--language=<language>"
syntax. Default language is set in tarantoolctl config file.
Usage:
tarantoolctl enter <app_name> --language=SQL
tarantoolctl enter <app_name> --language=Lua