Completed dialog documentation and exception messages.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@801 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Add basic command validation.

A command is only considered valid when it is syntactically correct
and includes an executable as first argument. Otherwise,
the dialog cannot be closed by pressing 'Save'.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@802 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Validate even when no file is currently loaded.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@803 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Wrap table into ScrolledWindow.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@804 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Insert menu items into menu shell and execute commands.

The menu is regenerated every time the list of commands is edited.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@805 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Allow executables residing in PATH.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@806 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Add F8 hotkey to start first external command.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@807 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Add documentation to ChangeLog.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@808 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Update translation template.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@809 6cf541bf-b722-4a7c-9fc0-fb1e75421f59
Update German translation.

git-svn-id: https://mcomix.svn.sourceforge.net/svnroot/mcomix@810 6cf541bf-b722-4a7c-9fc0-fb1e75421f59