Feature request: variables in tech base path

[klayoutmatthias]

For the full discussion see: https://www.klayout.de/forum/discussion/1370/homepath-in-technology-base-path#latest

[klayoutmatthias]

The solution implemented now allows using interpolated expressions inside the base-path:

• $(tech_name) -> substituted by the technology name
• $(tech_dir) -> substituted by the directory the technology file is stored in
• $(tech_file) -> substituted by the absolute path to the tech file
• $(appdata_path) -> substituted by KLayout's home directory (e.g. ~/.klayout)
• $(env('X')) -> substituted by the environment variable $X