RAISE_V*(), LOWER_V*(), VPP_BEFORE_VDD macros

* Added macros to make experimenting with other interface hardware easier.
 *   `RAISE_VPP()`, `RAISE_VDD()`, `LOWER_VPP()`, `LOWER_VDD()` call their `digitalWrite()` counterparts.
 *   `VDD_ON` and `VDD_OFF` complement `MCLR_VPP` and `MCLR_RESET` as a means to change Vdd from active-high to active-low.
 *   Previous behavior remains the default.
*   Added `VPP_BEFORE_VDD` define. When true (default), Vpp is raised before Vdd when entering program mode (this is the previous behavior). When false, Vdd is raised before Vpp instead.
 *   I needed to mess with this for my 16F88, probably due to an internal oscillator setting that needed to be cleared.