Fix for bug 1196.

This bug would cause the player to jump when jump was assigned to
Space and they closed a dialog with Space. I tested vanilla
MW for behaviour and found that Jump was the only basic input which
MW does not allow when closing dialogs (i.e. if Space is assigned to
move forward, MW will move you forward after closing the dialog).

There were two reasons for the bug:
1) OpenMW GUI does not consume UI events
2) Jump occurs so long as key is down (not only on first key down)

To minimally fix the bug, I made it so that keypress events can be
consumed by the GUI and not passed along to the player control
input manager (1). However, if the player holds space, they will still
jump (as the subsequent key held events will be captured and cause
a jump).

Unfortunately, there is no idiomatic way that I could find in the
OpenMW input manager to perform events only on key down. Instead,
I introduced a variable which tracks whether the jump key has been
pressed for the first time within the current frame (2).

Note: I was initially concerned that limiting the jump event to
KeyDown and not Key Hold would cause issues with swimming,
levitating, or variable height jumping. However, after a bunch
of testing in vanilla MW and exploration of the OpenMW codebase
I could find nothing suggesting the need to capture the jump
key being held.
Update in response to comments.

It turns out I was erroneous about problem (1) in my original commit
message. I thought that in an edge case the OpenMWGUI could both handle
the same event on the frame the GUI was closed. My test for
this was broken. So after brainstorming many possible unsatisfactory
solutions to this event handling, it's luckily not necessary!
1196/1217 fix

Fixes an issue where inputs could be processed by both GUI and
gameplay systems. An enabled/disable has been added to OIS
channels, and OpenMW now disables player gameplay hotkeys when
a GUI element has focus. GUI hotkeys are left enabled.
Merge branch 'master' into bug1196jumpdialog

Conflicts:
	apps/openmw/mwinput/inputmanagerimp.cpp
Cycle with equipped items if all slots are occupied (Fixes #1395)
Fix not reacting to quit request while video is playing
Use question mark for not found glyphs in the font
Work around missing character in french morrowind font (Bug #1390)
Fix crash when loading a savegame after dying (Fixes #1389)
Fix forced switch to third person on death not always working

For instance, when dying from fall damage
Add missing padding for item tooltip magic effects
Fix item weight displaying as 1e+3 for Stendarr's Hammer
Fix AiCombat being incorrectly added to player (Fixes #1356)
Refactor item icon code into ItemWidget (Fixes #1391)

 - Removed duplicate code
 - Fixed missing magic backgrounds during item drag&drop
 - Change background texture used for HUD icons
Don't use armor mitigation for fall damage
Don't block hits when in hand-to-hand combat (shield not visible)
Fix being able to place items on top of actors (Fixes #1403)
Allow opposite gender's parts as fallback (Fixes #1404)
Remove horizontal messagebox layout, not used in vanilla (Fixes #1402)
Fix alchemy allowing same item ID in different slots (Fixes #1407)