Fixed "runtime.hardware.path" and "runtime.platform.path" values

"runtime.hardware.path" now contains the path to the hardware folder
of the currently selected board and "runtime.platform.path" the path
to the specific platform.

This should fix #1176 and #1761.
Merge pull request #1790 from cmaglie/platform-paths

Fixed "runtime.hardware.path" and "runtime.platform.path" values