Add Text improvements

[paulba]

Just a couple of things to make the "Add Text" function a little nicer to use.

1. default the font size to a percentage of the image size, currently defaults to a font size of 10, so many times i'm working on a large pic and the font is not even seen. This would be great for infrequent non techo users as they would not keep adding text all over place until they realise there mistake or have consulted someone with experience. This pergentage would be good if it could be stored in the ini file.

2. In the processing "Add Text" has a position option, put this in the adhoc "Add text" to allow for consistency of placement.

Thanks

Paul