Demo app recipe cleanup

The evolution of the demo applications over time has resulted in the accumulation of some cruft and inconsistencies in their recipes.  This issue proposes the following cleanup:

• Remove remaining references to libhomescreen, qlibhomescreen, etc. as appropriate.  Some of this will be driven by related fixes to qmake configuration in the application(s).

• Update RDEPENDS to reflect current agl-service-* binding dependencies (the current lack of which leads to e.g. SPEC-3734).

• Update recipes to follow the OpenEmbedded style guide (https://www.openembedded.org/wiki/Styleguide)

• Update SUMMARY and DESCRIPTION fields to be consistent and drop references to "CES 2017".