cookie-expire-time

- document new cookie feature and configuration setting

- add configuration setting

- small refactoring in cookie handling
  - first manage cookie-expire-time
  - and next, cookie-timeout

- convert cookie to session-cookie if cookie-expire-time=0
- enforce expire-time if cookie-expire-time>0
Replace tab chars by four spaces in code.
manage --cmd argument multi-times on commandline

Allow starting vimb with multiple --cmd arguments on commandline.

- convert vb.config.autocmd to GList
- process all the list at vimb startup
- pass all the list to new process on opening a new target
- cleanup on exit
multi-cmd: update documentation
multi-cmd: use GSList instead of GList

the argument building (at launch time) is not optimal, as arguments are
appended (instead of prepended). But as it is a one shot per instance,
and there should not have lot of --cmd passed, it should be tolerable.
rename autocmd var, used for --cmd processing

rename vb.config.autocmd to vb.config.cmdargsi, which is a little bit
missleading cause of the autocmd feature.