digital: Fixes CID 1043266
blocks: Fix CID 1088839, 1046407 and 1046395
digital: Fix CID 1043270, minor refactoring
digital: Fixes Doxygen warnings, clearer docs.
modtool: Added example dir to encourage people to add examples
CID: Fixes 1046322

The constructor for fll_band_edge_cc_impl calls
fll_band_edge_cc_impl::design_filter which instantiated
two filter objects that were never freed
Merge branch 'maint'