Mac5120 (#283)

Mac5120 (#283)

* add generic qt installer for osx.

add travis builds with osx and qt 5.9.7, 5.12.0
update qtci extract-qt-installer from upstream.
add some error detection and debug to travis_install_osx, travis_intall_linux_local.

* catch qtci/install-qt up with upstream.

* try harder with early extract-qt-installer bugs on osx.

* don't source travis qt install scripts.

* fix caching for travis.

* qt installer improvements

validate installs
add debug for failed installs

* update travis osx qt 5.12 build to 5.12.1.