Added basic text box feature
Added basic text box feature

Added a basic text box feature, to add simple text (in one of the 14
standard PDF fonts).

The text box creates a box, optionally fills the box (with or without a
border), and prints text within the box.

overflow text is visible.

kruszczynski/combine_pdf,shibocuhk/combine_pdf,nathanl/combine_pdf,boazsegev/combine_pdf,workshare/combine_pdf