*/kf5-*: (KDE Frameworks) lighten dependencies

- ECM (extra-cmake-modules) is only ever a build-dep and was missing
  in some places where it was previously pulled in implicitly
- Qt testlib is only a build-dep

While here
- conventionally, the _build and _run items in USE_KDE and USE_QT
  are sorted to the end, and they start a new line in the Makefile
- remove tcberner's created-line (confirmed on IRC)
- use DISTVERSION everywhere
- reduce inter-framework dependencies using the tooling proposed by
  tcberner in https://reviews.freebsd.org/D27304

Some PORTREVISION may have jumped by more than 1, since this commit
is a squash of a long string of updates where I may have bumped a
port once for ecm_build, and a second time for other lightening-up.