added browsable and socket option features

[kongkrit]

I added two features:

1. ability to make a share browsable or not by the show flag in -s parameter
   this changes the syntax for -s from

-s name:path:rw:user1[,user2[,userN]]

to

-s name:path:show:rw:user1[,user2[,userN]]

if show is any other word (like hidden), the share will not be browsable.

2. ability to remove socket options line from [global] section of smb.conf. having it there caused slow transfer for my use case.