add a clangd and qtcreator make targets

Add a clangd make target:
$ make clangd
This installs a .clangd file with configuration (includes/macros/compiler flags)
for the clandg language server.

Add a qtcreator make target:
$ make qtcreator
This installs a .qtcreator directory with QTCreator IDE project files.
In the QTCreator you can open a project by selecting the .qtcreator/pikotools.creator
file.

You can use 'make qtcreator' again to refresh .qtcreator/pikotools.files,
the rest of the project files will not be modified.

.templates/.qtcreator/pikotools.files

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