Generate CMake toolchains from Python code

[ruslo]

Use toolchains table from https://github.com/ruslo/polly/blob/master/bin/detail/toolchain_table.py to generate actual CMake code:

• Generate name of the toolchain file
• Generate human-readable toolchain name
• Include CMake modules automatically
• ...

[ruslo]

Add HUNTER_TOOLCHAIN_UNDETECTABLE_ID automatically