cpplib: Add transposed vector accessor to Mat4

Although this version does not allow modification of the matrix via returned reference,
they are very handy.
Merge branch 'cpplib' into next2
Make use of new cpplib::Mat4::tvec3() in GLwindowSolarMap::drawMapCSOrbit
refactor: Erase ancient codes that will never be used even for reference
Add getter method for orbit center body of OrbitCS
Make OrbitCS::flags2 hidden inside the class and added accessors for it

OrbitCS::{get|set}ShowOrbit() provide access to the flag.
The flag is not necessarily a bit field since the implementation details
are hidden from the public.

Also enabled solar map to display orbit ring for binary system.
Fix delegation of unhandled stellar file event to a script

Previously, an unhandled stellar file directive is transferred to
a Squirrel function ::CoordSys.readFile[0], which itself looks confusing.
It also lead errors by unclear reason.

Now we define the scripted function simple and straightforward way;
it's named stellarReadFile.
Move hard-coded rstation processing logic for stellar file to init.nut

The Resource Station is one of a few classes that can be defined in the
stellar structure definition files.  The logic is hard-coded into
CoordSys::readFile(), but it's best implemented in a script for easy
customization.

The hard-coded logic is commented out anyway.
Separated RStation-draw.cpp from RStation.cpp

Also added Doxygen comments on top of each files.
Make RStation be rendered visible

The class have not had a model to show, because it has been stuck with
precompiled .bin files which are obsolete.
Add an initialization script for RStation

The added script is RStation.nut.

Overlay icon fo RStation objects are added, too.
Add maxRU and defaultRU variables to RStation's initialization scirpt
Add modelFile parameter to RStation's initialization script
Delete obsolete and commented out codes from RStation
Add maxOccupyTime variable to RStation initialization script

The alphacen.nut mission demonstrates it.
Add "ru" (Resource Units) to Squirrel interface of RStation

Also revived property window's ru amount display.
Prevent TextureSphere from trying to load texture file name of null string

It's possible that we have a placeholder TextureSphere object with absent
texture file in prototyping phase.
Erase texture definition of Alpha Centauri's planet

The texture image is going to be prepared.
Add getStatic() method definition to RStation

It's required for omitted classname() to work properly.
Add buildBodyByHitboxes() to ModelEntity to share for multiple Entities

The btShape and btRigidBody construction with a list of hitboxes are
so common that it appears dozens of times.

We have not shared the code because many classes share a shape among
its instances, but we shouldn't repeat the same codes just for this
reason.

The original source is moved from Destroyer::buildBody().