Harmonization of UI messages

[Michael Schmitt]

Dear Martin and Angus,

I changed a couple of messages (mainly concerning the Box dialog) to 
"harmonize" the dialogs. Could you please check and apply the patch? 
Thanks in advance.

Could you please also have a look at the Box dialog (I don't use xforms) 
and check that colons are used consistently? ("Height" vs. "Height:") I 
guess a few are missing. This might save us poor translators another few 
messages.

Kind regards,

Michael