Fixes: lp:1492577 (and probably also lp:1672116).
*https://bugs.launchpad.net/kicad/+bug/1492577
*https://bugs.launchpad.net/kicad/+bug/1672116
- Fixes a race condition causing the wrong page to be selected in
`OnPageChange`
- Allows the validate path and browse button to refresh the
template page even when the path was not changed. This is needed
since on OSX the page needs to be active for the templates to be
rendered.
Also add PAD_SHAPE_<PADSHAPE> equiv to PAD_<PADSHAPE> and PAD_ATTRIB_PAD_<PADATTRIB> equiv to PAD_<PADATTRIB>
(<PADSHAPE> = ROUND, RECT... and <PADATTRIB> =SMD, CONN ... )