Added manual rotation of the ship rotation as discussed in issue #1156.
It is toggled on and off by a toggle button in ShipInfoCard. When in
manual rotation mode:

* Ship rotates up to certain speed. It keeps its motion until changed.
* When changing the speed of time flow, rotation is not stopped or
changed.

I'm new to this, so please tell me if I did something wrong, I'll try to
improve it next time.
Some corrections to manual rotation idea, issue #1156
* Time cannot be accelerated if rotating fast.
* Toggle button for manual rotation moved to constructor where it
probably belongs.
* Manual rotation works only in Manual control mode, this is ensured by
adding argument manualRotationAllowed in PollControls.
Some fixes:
* Thrusters were over-sensitive in higher time acceleration mode. Fixed.
Ang. velocity capping added also in manual rotation mode. However, if
you spin the ship in slower time acceleration mode and then switch to
higher one, ship does not slow itself - it would look weird.
alpha to all system objects
Mapped toggle manual rotation state to key 'r'. The button added as
proper member of the class.
Small change in autopilot FlyTo command, which makes autopilot turn
thrusters off if low on fuel and if the speed is too high to slow down
afterwards.

Added two functions to Ship.cpp, one return the effective propellant
escape velocity and the other returns how big veocity can be reached
using of X fuel (according to Tsiolkovsky rocket equation).
>RGB>Alpha
Proper destructor for ToggleButton and Labels in ShipInfoPage.
Undo the destructor, it caused game to crash when ExitGame was pressed,
instead of going to the main screen. (Why?)
undo + alpha for planet background
star_a
star_a_giant
star_a_hyper_giant
star_b
all stars
Cosinus works better. It is a bit worse numerically, but with sinus,
the autopilot may turn thrusters off when heading in exactly opposite
direction. (Which can happen e.g. if you overshoot the space station.)
Even better fuel saving, because:
* if the ship is still far, the direction matching is not so strict
* not speeding over maximal speed when correcting the direction
Allow multiple government types to be added to a Faction

Lua Faction:govtype now adds the govtype to the Faction's govtypes list
rather than changing the faction's sole govtype.
Custom systems are now included in the first faction that has the
system's govtype in its list (essentially no change)
Standard systems take the first govtype of the faction they are a member
(used to take the Faction's sole govtype, taking the first was the
simplest for me to implement).
Federation Faction definition now includes 'Earth Colonial Government'
as well as 'Earth Democracy'. This should bring Barnard's star back into
the Federation fold.

Conflicts:
	src/Factions.cpp
Clean-up of Faction usage in Polit

Crime and legality methods now use StarSystem->GetFactionIdx() rather
than looking it up index via a link from govType retrieved from
StarSystem->GetSysPolit()
Removed Faction index from politDesc_t
Moved SysPolit::GetAllegianceDesc to StarSystem::GetAllegianceDesc
Pick System's govType randomly from Faction's govType list

No longer always picks first (last?) in the list.
New Faction::RollGovType method taking an MTRand makes the selection
(May need renaming?)
Removed code for setting get CustomSystem's based on its govType.
Added factionIdx member to CustomSystem in preparation for enabling
setting of CustomSystems Factions from Lua.

Conflicts:
	src/Factions.cpp