- fixed bug #216, #217, #218
- make 'colorshell' no longer pollute PS1...4 variables
- Don't mark setting's name and a few others as translatable strings.
- ove last command recording to the end of BashStyle-NG initialization
- Less environment pollution by unseting a lot of variables which are of no use after @code{BashStyle-NG} initialization.
- Simplified color setup mechanism for non/echoable prompt part colors.
- minor coding style changes / improvements