plainbbcode update

[mumuri]

plainbbcode allow you to add bbcode button in your template

but in some case, you don't want to display all the options to the user

For instance in the header of an article,if you don't want that the user put a picture,

plainbbcode image=no

Note that for the 3.0, you can add
plainbbcode extraplugins=no

for the customized version of a given plugin