Rework weapon scheme handling in frontend and fix a couple of bugs There were many oddities in weapon scheme editing which are fixed now: * When you left the weapon scheme editor, everything flashed briefly * When you leaft the weapon scheme editr, the weapon scheme selection always reverted to Default. Very annoying * Clicking on New or Copy now instantly creates and save the new weapons set

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Lua scripts for engine testing. These scripts are the same as other Lua scripts

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in Hedgewars, but you ought to call `EndLuaTest(TEST_SUCCESSFUL)` or

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`EndLuaTest(TEST_FAILED)` when the test is completed.