This patch enables math expression evaluation for most of the text input
controls in pcbnew.
NEW: pcbnew text input controls are able to evaluate simple
mathematical expressions, including distance units (e.g. 5.0+(2*1.2mm)).
* Adds a "Grid Reference Point" to the VRML export; this allows a user to specify the (X,Y) coordinate which will be the origin point on the output
* Adds a "Grid Reference Point" to the IDF export; this is similar in purpose to the corresponding VRML export feature.
* Make generate button the default in Eeschema netlist dialog.
* Fix spacing issues in export IDF dialog.
* Make OK button the default in export IDF dialog.
* Remove unnecessary end dialog code from export IDF dialog.
* Improve resizing of export IDF dialog.