Vectorization in Default Kernel Creation Driver

Reintroduce vectorization into the default create_kernel driver.

• Encapsulate the driver into a class structure
• Update vectorization options and parse deprecated cpu_vectorize_info options in CreateKernelConfig
• Add automatic vectorization in the kernel creation driver

Fixes on the side

• Remove late constant folding in create_kernel; fold indices in LowerToC instead
  • This is required because at this late point, the AST may contain intrinsics, which the constant folder cannot handle
• Clarify some docstrings and exception strings
• Extend domain kernel test cases with vector targets

Closes #108 (closed)