ECM find modules

[Alex Merry]

If you have find modules that you think should go into
extra-cmake-modules 1.0.0, mention them in this email thread.

I would like to have a rule similar to the old kdelibs rule for classes:
at least two users, otherwise you may as well just put them in the
project's local cmake directory.

I did a quick search using

find . \( -path ./cmake-git -o -path ./qt5 -o -path \
./kdesupport/extra-cmake-modules -o -path ./kdelibs-frameworks -o \
-path ./frameworks/kde4support -o -path ./kdesupport/strigi -o \
-path ./kdesupport/phonon -o -path ./kdesupport/qca -o -path \
./poppler -o -name .git \) -prune -o \
-name Find\*.cmake -exec basename \{\} \; | sort | uniq -d

(Phonon, Strigi, QCA and Poppler don't use ECM) and got the following list:

- FindDBusMenuQt5.cmake
knotifications and workspace (appmenu, statusnotifieritem dataengine)

- FindKDevPlatform.cmake
kdevelop and its plugins; should use Config.cmake files instead

- FindPolkitQt-1.cmake
kauth and (bizarrely) polkit-qt-1; already ships a config file that
should be used

- FindQJSON.cmake
kdevplatform, libdbusmenu-qt and workspace: QtCore includes this
functionality, so shouldn't be needed

- FindSqlite.cmake
twice in quality-kde-org; ignore?

- FindUDev.cmake
solid and workspace (powerdevil)

Alex