converter/ibm_terminal Refactor and Configurator support (#4414)

converter/ibm_terminal Refactor and Configurator support (#4414)

* IBM Terminal converter: layout macro refactor

- Renamed KEYMAP to LAYOUT
- Renamed KEYMAP_101 to LAYOUT_101
- minor matrix array fixes

* IBM Terminal converter: default keymap refactor

- Updated layout macro names
- Updated to #include QMK_KEYBOARD_H
- config.h updated to use #pragma once

* IBM Terminal converter: priyadi keymap refactor

- Updated layout macro names
- Updated to #include QMK_KEYBOARD_H
- Removed redundant KC_TRNS and KC_NO defines
- config.h updated to use #pragma once

* IBM Terminal converter: Configurator support

* IBM Terminal converter: readme cleanup

Updated markdown formatting.

* IBM Terminal converter: readme rename

Renamed file to fully lowercase.