* 1) added J. Villars code from PR#238 (https://github.com/myhdl/myhdl/pull/328) to augment the `@block` decorator with arguments, initially to keep the generated names simpler especially when nesting `block`s without adding *hdl* code - I modified it a bit using `skipname=False` rather than `keepname=True` as default
2) added _hdlclass.py to support Class Based Design, look at bot test/conversion/general/test_hdlclass.py and test/conversion/general/test_hdlclass2.py
This needed the changes of 1) above.
* 1) _Signal.py
added property `.nbits` for use in HDL iso `len(sig)`, anticipating Structure and Array where `len()` is not what `.nbits` will give you ...
added `duplicate(value=None)` method to avoid that ugly `newsig = Signal(oldsig._val)`
2) _block.py
minor changes
3)_hdlclass.py
removed ForwardPorts resolution as this currently adds a *stray* sig in the .vcd output - even if noe ForwardPorts are present
cleaned the code to what is actually working
4) _traceSignals.py
The `@block(skipname=True), which is heavily used in Class Based Design, applies `None` as that block-name and this will show up as an additional level in the .vcd which looks ugly and distracting.
So reworked this file to skip adding the None-level
Also added indents in the .vcd var section, primarily for debugging, but kept this as it looks nice.
Introduce f'strings
5) _analyze.py
changed UPPER_CASE naming of processe/always into lower case, making the generated signals conform with the producing process/always
6) test_xxxx.py
changed @instance with *logic* as function name into *comb* as `logic` has become a reserved Verilog keyword
* cleaned test/bugs
replacing generator names *logic* and *output* with *comb* as `logic` and `output` have become Verilog reserved keywords
* replacing more occurrences of *logic* by either *comb* or *synch*
* one *comb* too many :(
* added small test_hdlclass0.py to help in debugging
updated the 'doc' section -- needs publishing
added direct conversion of Class Based Design modules - resulting in lesss boiler-plate code
