main : alternative instruct mode (Vicuna support, etc.) (#863)

* Add support for configs, add configurable prefixes / suffixes, deprecate instruct mode, add stop prompt

* Add multiline mode, update text input.

* bugfix

* update implementation

* typos

* Change --multiline implementation to be toggled by EOF.

* bugfix

* default multiline mode

* add more configs

* update formating

* update formatting

* apply suggestions

configs/alpaca.txt

@@ -0,0 +1,9 @@
+--clean-interface
+--interactive-first
+--keep -1
+--ins-prefix-bos
+--ins-prefix "\n\n### Instruction:\n\n"
+--ins-suffix "\n\n### Response:\n\n"
+--reverse-prompt "### Instruction:\n\n"
+
+-p "Below is an instruction that describes a task. Write a response that appropriately completes the request.\n"