new solver options: SocketCommand and NameCommand (patch by
<C.Stott@surrey.ac.uk>)

bring option docos up-to-date

Set View.ShowTime=2 to show the time value even if the view contains a single
time step..

typos

update for gl2ps

update option doc

Add DisplacementFactor option + rename ArrowScale->ArrowSize and
ArrowType->VectorType

Small corrections

Corrections apres relecture / part 1

More work on chapters 1 and 2. Should be mostly OK now.

Major rewrite of the Overview section + web page

small updates

... in @node confuses makeinfo

Added "gmsh -doc" to automatically generate the texinfo documentaion
for all the options.