t.rast.list: Add CSV, JSON, YAML outputs (OSGeo#2258)

* This adds CSV, JSON, and YAML output and generalizes the other outputs.
* Method is now meant only for different data gathering methods, not for the output formatting. method=cols and method=comma are now obsolete.
* All formatting is available with all methods.
* Most code is shared between the two main branches of code (simple list versus delta/gran methods code).
* Columns can be now specified for any option (previously only for cols/list and partially for comma/line output).
* The change is backwards compatible both on module interface level and on Python API level.
* Activate and fix old bash test (-i by t.register is not accepted without start_time).