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.

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

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

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

added a variable @PROJECT_NAME@_PREFIX and use it as the required variable to make a nicer output when depending projects find this package

removed @PROJECT_NAME@_LIBRARIES from the required variables since the package might not provide a library

Use FindLibrary() cmake command to properly locate the library, even if the directory is already known. This is needed to get the proper full path reference to the library.

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)