Keyboard: Initialize pointers to NULL.

It's good practice to always initialize pointer member variables
to null. We had couple of pointers un-initialized in keyboard
class.
Keyboard: Use xkb_state_mod_*_is_active to determine modifier state.

We currently use xkb_state_serialize_mods, to determine the current
state of modifiers. As per xkb documentation, regular clients should
not be using this but rather prefer xkb_state_mod_*_is_active api.
The patch makes changes in this direction.
Keyboard Style fix: Put each argument on a separate line.
Keyboard: No need to query for modifier state on every OnKeyNotify.

We query for modififer state for every OnKeyNotify, which seems
redundant. Instead it should be enough to do this in OnKeyModifiers.
Keyboard: Add support for CapsLock.
Keyboard: Replace deprecated xkb keysyms.
Keyboard: Don't create a new key event in DRWH.

DRWH is responsible for dispatching key events to delegate.
Instead of using the current event, we construct a new key event.
This seems unnecessary and also any character information is not
copied in this case(causing unnecessary re-calculations). This
CL changes so that, we re-use existing event instead of creating
new one.
Keyboard: Add ENUM defines for Character and Action key codes.

This patch adds enum defines for characters and Action keys.

Characters: This is a standard ASCII set.
Action Key: Any key which results in certain action.
            i.e. Delete Key.

This would help unify Keyboard code defines between oz-wl and
Chromium. It would also support easy extension of various
Key combination. These will be taken into use in follow
up patches.
Keyboard: Add support for XKBKey and Character codes.

This patch implements necessary support for mapping xkb
keycodes to ozone types. This support is implemented in
KeyboardEngineXKB. The class will be taken into use in
coming up patch.
Keyboard: Add GetCharacter Support.

This patch adds support for converting character types by taking
into account the current modifier settings and also setting the
correct keycode type.
Keyboard: Keyboard should internally use KeyboardEngineXKB.

This patch makes changes in Keyboard class to take KeyboardEngineXKB
into use. Keyboard should be only implementing the wayland callbacks
and let keyboardengine handle the actual processing of key events.
Keyboard: GetCharacterCode while handling KeyNotify.

This patch takes into use the helper functions
KeyboardCodeFromNativeKeysym and CharacterCodeFromNativeKeySym
to set the correct KeyCode and CharacterCode for every KeyNotify
event.
Keyboard: Remove kbd_conversion.

This CL removes kbd_conversion.cc and kbd_conversion.h as they
are no longer in use.
Add Owners file to ui.