PixelCNC v1.10a release: metric project option, outline operation toolpaths, and miscellaneous.

v1.10a is up, and existing owners should be able to download the new paid version. Everybody else can download the trial version and test out the metric functionality. Go into Config->CNC/CAM Settings and click "Units of Measure" to toggle between inches/millimeters. The option is strictly used to determine what measurement system new projects should be created with. A project's units of measure cannot be changed. Loading a project of a different measure units than the user has configured will result in PixelCNC temporarily running in that measurement system until a new project is created or a different one is loaded. Most users will likely set this and never touch it ever again ;)

The new outline toolpath operation allows the user to specify a cutoff value along the image grayscale spectrum that the delineation between light/dark areas should lie, and thus the 'outline' that separates them. From this boundary the toolpath can be offset using a positive or negative cut step value, which indicates the physical distance from the outline to offset the toolpath into the lighter (positive step value) or darker (negative step value) sides. The outline toolpath cut itself will achieve a maximum cut depth as set by the 'Max Depth' operation parameter, in cutting pass depth increments of 'Cut Depth' - following the same convention as the existing operations from v1.00a. Naturally the cut depth is limited only by the flute length of the chosen tool definition (or by the physical imitations of the CNC itself!)

Also, PixelCNC now has backwards compatibility for project files created using older versions. Being that v1.00a did not support metric this means that all projects from that version will forever load as an imperial measurement system project, even after re-saving with v1.10a per adherence to projects' measurement system being established upon creation (i.e. File->New Project, or whatever measurement mode PixelCNC was in when the project had an image/tools/operations created.)

Various other little changes have been made and can be found in the changes.txt that is now included with each release.

Any and all feedback is welcome!