Speedup init of scans

This MR speeds-up the init of scans (2-3 seconds), which is mainly (> 95%) defined by the chip object, by:

• Using a faster c-parser for yaml if available. If you install pyyaml using conda it is available.
• Not creating all mask shift patterns on chip init. Since scan usually only uses one pattern.

Also makes file names unique #445 (closed) and tests less likely to fail due to open files.