- added new VM instructions to access the constant tables with a variable index.
- refactored VMFunctionBuilder's constant tables so that they are not limited to one entry per value. While this works fine for single values, it makes it impossible to store constant arrays in here.
This also means that for now Lua-style multi-assignments are disabled, those should be easy to enable by making some changes to the assignment_statement grammar so that it doesn't recognize single assignments, but for now this is low priority because it adds a significant amount of complexity to do this right with functions that have multiple return values.
* everything related to scripting is now placed in a subdirectory 'scripting', which itself is separated into DECORATE, ZSCRIPT, the VM and code generation.
* a few items have been moved to different headers so that the DECORATE parser definitions can mostly be kept local. The only exception at the moment is the flags interface on which 3 source files depend.
