adds initial set of Flex Turning Lane RULs

This is a prototype with limited functionality. There is full support for
LHD though, but compiler version 1.0.2+ is required.
changes FTL-IIDs to new scheme
Merges Alex's Ave-FTL code with Road-FTL code

In particular, fixes of commit 033d9e80 are properly restored.
A few FTL overrides may have been replaced by mine.