* Add defaults to MANIFEST.SKIP

This adds a few forgotten items and obsoletes a few old entries.

* Remove unused dependencies

* Change the flow of the FreeBSD installation instruction

The sections are fewer, longer and more focussed.

* Use bullet list for databases

This opens up for lowering the operating system headings to level 3,
which is structurally correct.

* Remove stray sudo

* Update database configuration instructions

* Engine installation instruction has been renamed

* Rename installation instruction

* Update document structure

* Update wording

* Use PostgreSQL 9.5 in FreeBSD instruction

I failed to install p5-DBD-Pg together with any other version of
PostgreSQL using pkg.

* Report component version number

* Don't mention newer things we don't support

* Rename Installation.md in MANIFEST