Makefile: explicitly list which example capture subdirs to install

Makefile: explicitly list which example capture subdirs to install

Commit 4fafe8159940 as of 2012-05-14 introduced a simple "make install"
target. The asterisk wildcard and the additional Makefile "negation" use
to work for clean checkouts, but are considered too greedy a pattern for
locally modified work areas during development.

Explicitly list which subdirs to install to the filesystem. Which
improves robustness, avoids clutter, and is considered acceptable
maintenance overhead since adding more top level directories should
be rare an event. The explicit list is also easy to trim down should
developers want that during local work.

Phrase the subdirectories list such that users can specify additional
items in the "make install" invocation.