In log4slime split the time and thread name regexp's and relax thread one slightly

[7max]

Currently everything between debug level and package, needs to match log4slime-time-regexp, including thread names. And it seems weird characters in thread names are more common then anticipated.

Split the regexp into two, one for date/time, and one for thread part, and relax the thread/ndc regexp, so it can handle most punctuation

Also change them to (defcustom) instead of defvars.