Remove the Accessibility Tab completely from the app (#79)

See
https://github.com/OpenVR-Advanced-Settings/OpenVR-AdvancedSettings/issues/27

The Accessibility tab was made redundant with the implementation of the
new playspace/room/universe tab in
https://github.com/OpenVR-Advanced-Settings/OpenVR-AdvancedSettings/issues/60

The tab inherited from the PttController class, which required changes
in order to work with the new IVRInput system. See
https://github.com/OpenVR-Advanced-Settings/OpenVR-AdvancedSettings/issues/51
for more about the IVRInput system.

Removing the page now at an early state is going to make it easier to
refactor the PttController since only one class is inheriting it,
instead of two. Since the Accessibility tab is going to be removed
anyway, it makes sense to remove it now.

Readme.md

@@ -22,7 +22,6 @@
  >   * [Audio Page](#audio_page)
  >   * [Revive Page](#revive_page)
  >   * [Utilities Page](#utilities_page)
- >   * [Accessibility Page](#accessibility_page)
  >   * [Statistics Page](#statistics_page)
  >   * [Settings Page](#settings_page)
  > * [How To Compile](#how_to_compile)
@@ -260,12 +259,6 @@ Any changes to controller settings are immediately applied by Revive (Requires R
 - **Steam Desktop Overlay Width:** Allows to increase the size of the Steam desktop overlay. Useful for multi-monitor setups.
 
 - **Media Control Keys:** Allows controlling a media player through the media keys. This is the same as having a keyboard with media keys and then pressing them. Should support most common media players.
-<a name="accessibility_page"></a>
-## - Accessibility Page:
-
-![Accessibility Page](docs/screenshots/AccessibilityPage.png)
-
-- **Adjust Player Height:** Offsets the player height to allows short or wheelchair-bound players to fully interact with height-limited applications by both boosting their height and being able to touch the in-game floor when necessary by pressing a configurable motion controller button.
 
 <a name="statistics_page"></a>
 ## - Statistics Page: