plot(mode=...)

[marco-mariotti]

Introduce a mode argument to plot() which effectively preprocess data and activates other options, to achieve a certain visualization type.

First example of mode = 'gtf' or something, which looks for gene / exon / CDS Features, and prepares thickness, depth etc to obtain a UCSC like visualization. This will replace 'thick_cds=True' and can grow to offer more functionalities.