Revise carvac_dv keymap for easier alt-tab (#1871)

* Add carvac_dv keymap for mitosis

* Add mouse keys

* move backspace, etc, and fix tab

* remove commented-out functions in keymap

* Fix scroll buttons and add left/right scrolling

* Make num momentary, add comments, and clean up

* fix mouse scroll acceleration

* Add tab, remove bksp, move print screen

Having tab next to control and alt makes for much easier
alt-tabbing and ctrl-tabbing.

That displaced print screen, but I had never used the non-layer
backspace on the right hand, so I moved printscreen over there.

keyboards/mitosis/keymaps/carvac_dv/keymap.c

@@ -35,7 +35,7 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
  * |--------+--------+--------+--------+--------||--------+--------+--------+--------+--------|
  * | Z      | X      | C      | V      | B      || N      | M      | ,      | .      | /      |
  * '--------+--------+--------+--------+--------||--------+--------+--------+--------+--------'
- *          | PGUP   | PSCR   | LCTRL  | SPACE  || LSHIFT | ENTER  | UP     | BACKSP |
+ *          | PGUP   | TAB    | LCTRL  | SPACE  || LSHIFT | ENTER  | UP     | PSCR   |
  *          |--------+--------+--------+--------||--------+--------+--------+--------|
  *          | PGDN   | LGUI   | LALT   | FN     || NUM    | LEFT   | DOWN   | RIGHT  |
  *          '-----------------------------------''-----------------------------------'
@@ -45,7 +45,7 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
   {KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,           KC_Y,    KC_U,    KC_I,    KC_O,    KC_P    },
   {KC_A,    KC_S,    KC_D,    KC_F,    KC_G,           KC_H,    KC_J,    KC_K,    KC_L,    KC_SCLN },
   {KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,           KC_N,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH },
-  {XXXXXXX, KC_PGUP, KC_PSCR, KC_LCTL, KC_SPC,         KC_LSFT, KC_ENT,  KC_UP,   KC_BSPC, XXXXXXX },
+  {XXXXXXX, KC_PGUP, KC_TAB,  KC_LCTL, KC_SPC,         KC_LSFT, KC_ENT,  KC_UP,   KC_PSCR, XXXXXXX },
   {XXXXXXX, KC_PGDN, KC_LGUI, KC_LALT, MO(_FN),       MO(_NUM), KC_LEFT, KC_DOWN, KC_RGHT, XXXXXXX }
 },