utils.lua: Add an inherits function to ease OO development

This will get used in #1719 to implement lua-side hyper{drive, space,
jump}.
utils: inherits: Add a "name" parameter
Merge remote-tracking branch 'origin/lua_inherit'
New BaseSphere parent, GasGiant derivaed and GasGiant shader, materials files.
Adding new files to Pioneer and Graphics projects.
Integrate and use new BaseSphere, GasGiant and materials.
Update the Linux auto-make files.
auto-commit: translation updates
don't initialise sector cache at start, temp workaround for #2802
don't try to render the glyph if there's no bitmap to render. fixes #2804
auto-commit: translation updates
Properly handle move of default-constructed (empty) JobHandle. Fixes #2802.
Bring some more functionality into the BaseSphere class, mostly static methods to take the implementation details out of Pi.cpp
Then delay generating the GasGiant textures until they're either visible or a reasonable period of tie has elapsed.
auto-commit: translation updates
auto-commit: translation updates
Change the default delay before generating the gas giant textures to 60 seconds instead of 5. 5 is ok on my hilariously-fast PC, not so much on others!
Remove a static member, it's two methods, it's increment and a couple of unused variables.
Create a small placeholder texture for the planet so there is something to see right from the start.
Merge pull request #2803 from fluffyfreak/gas-giant-planB

Merging Gas Giant rewrite.
Gas Giant rewrite (#2803)