EMI: Fix display of "dock" video

During the run of the "dock" video (first arrival at melee island) only
a black screen was displayed although the sound did work.
The lua code dims (_dimLevel = 1) the scene before showing a video so
that only the video is visible. GfxOpenGL::drawBitmap sets the current
color according to the dim level before it starts drawing the bitmap:

glColor3f(1.0f - _dimLevel, 1.0f - _dimLevel, 1.0f  - _dimLevel);

If there is no other glColor* call before drawing the video, the current
color stays (0, 0, 0) and the video won't be visible.

The bug fix resets the color to (1.0, 1.0, 1.0) after the drawing of the
bitmap at the end of GfxOpenGL::drawBitmap.
EMI: Fix turn_rate of voodoo chair

The turn rate for the chair of the voodoo lady is set to 1 in the lua
code which makes the turn animation very slow (> 30s).

Since the rate value of 1 is not used otherwise in EMI, adjust the
turnrate in this case.
Merge pull request #763 from inguin/emi-fixes

EMI: Savegame fixes
Merge pull request #764 from chkr-private/emi-fixes

EMI: various small bug fixes
GRAPHICS: Fix off-by-one error in software renderer
EMI: Fix color of menu entries

The highlighted menu entry is sometimes not correctly colored.
There are multiple textObjects per string (one for each color) and
residualvm draws them in an unspecified order.

To ensure that the correct textObject is drawn on top, each
object gets a layer attribute assigned by the lua code.

The patch adds the layer attribute to the runtime engine and orders the
textObjects by layer before drawing them.
Merge pull request #765 from chkr-private/menu-text-fixes

EMI: Fix color of menu entries
EMI: Fix actor orientation

EMI uses a different coordinate system than Grim, so we have to switch
dimensions in various places to share common code for walking and turning
actors. This patch fixes several yaw angle sign errors causing actors to
look into wrong directions.
Merge pull request #767 from inguin/emi-actor-yaw

EMI: Fix actor orientation
GRIM: Add a const_cast as making ts const is not worth the effort
EMI: Select the correct turn chore

In EMI's coordinate system, other than in Grim, actors turn right when
the yaw angle is increasing. Select the correct turn chore for the turn
direction.
EMI: Allow resetting actor turn chores

EMI scripts use nil in SetActorTurnChores() to reset the turn chores,
e.g. when Guybrush picks up the hot coal in wed.lua.
EMI: Restart turn chore when changed mid-turn

When the turn chores are changed while an actor is turning the current
chores will be stopped but the new ones won't be started until the turn
direction changes. This can be seen when hitting the run key while
Guybrush is turning.