* project-template: use lib install dir defined by GNUInstallDirs

this should fix library search problems on Tumbleweed
project-template installs cmake-config files to library destination
note, individual projects also need to be changed, for installation of actual libs

This provides ChimeraTK::<project-name> as cmake imported target.
Variables <project_name>_INCLUDE_DIRS, <project_name>LIBRARY_DIRS, <project_name>_LIBRARIES, <project_name>_CXX_FLAGS, <project_name>_LINKER_FLAGS are provided for compatibility but are generated from cmake-exports where possible and cmake imported targets should be preferred.

* provide function for option array conversion
to be used with target_compile_options etc + FindPackage results, where
findPackage results are of incorrect/old format

* FindDOOCS:
 - DOOCS components as imported targets
 - clean up no longer needed tweaks
 - add timinglib as component
 - make use of log levels and respect QUIET argument

* add_dependency: fail on wrong add_dependency usage
this was unseen since it worked in most cases but in general does not
in particular was causing trouble with imports from cppext
second arg must be version number

* pkgconfig exports
 - generated from cmake-exports
 - make linker flags come before libs, order is required e.g. for --no-as-needed flag
 - remove duplicates in output

* FindGccAtomic
- do not put absolute lib path in output since it was causing trouble with yocto builds. Should be in system lib
paths anyway. Also, make GccAtomic variable output name more consistent.

If a header-only library requires linking a 3rd party library, the ..._LIBRARIES variable could not be used in depending projects, because it
contained NOTFOUND.

THis is necessary for newer Boost (1.71) which puts the exported targets
in Boost_LIBRARIES. If we export that verbatim it causes link issues on
projects using the config scripts from Make

This reverts commit e7294d81.

This does not exist on xenial yet

find_package is for use inside the *Config.cmake files

To add public dependencies to the generated config, use e.g.

list(APPEND ${PROJECT_NAME}_PUBLIC_DEPENDENCIES "Boost COMPONENTS system thread chrono")

fix issue that a double "-l" can appear in the Makefile config shell scripts for libraries which already contain the -l

This reverts commit 7eace484.

GNUInstallDirs doesn't really deliver the intended directories. CMAKE_INSTALL_LIBDIR e.g. points to lib/x86_64-linux-gnu on Ubuntu 16.04

Fixed the confusing and inconsistently used names *_LINK_FLAGS and *_LINKER_FLAGS by always setting and getting both variables

- Quotes around input variables when doing string replace avoid existing semicolons from being deleted.
- The project target library itself was missing in the linker flags.

fixed issue with compiler/linker flags being interpreted as lists and thus having semicolons in between

${PROJECT_NAME}_CPPFLAGS -> ${PROJECT_NAME}_CXX_FLAGS
${PROJECT_NAME}_LDFLAGS -> ${PROJECT_NAME}_LINK_FLAGS

also make sure that the exported lists are consistently space-separated (sometimes they might be semicolon separated or mixed)