Remove unnecessary command for installing header files

Removing export statements and shell-invocations improves performance. The
specific install command for headers files was not required.
Move Qt meta and ui commands to build makefile

These commands are only used during build stage and need not be defined in the
main makefile. This results in less export statements that should improve
performance.
Move doxygen command to build makefile

Usage of doxygen is only required in the build makefile. Results in yet one
less export in the main makefile.
Move commands for rpm building to build makefile

Rpm building is relevant in meta mode as well but calling the build stage from
meta stage when command rpmbuild is missing will now result in a relevant
error message rather then a "no such target" as was the previous case.

Condition if an rpm-target is called is used for minimizing make code, expcept
for clean targets for intermediate rpm-files.
Move more commands to build makefile

Creating soft links are only required during library creation and not in the
meta stage. Awk is only needed when building rpm packages and can therefore be
hidden together with the rpm commands. Find is used for cleaning targets but
those are only executed in the build stage.
Refactor cppcheck feature and move command to build makefile

The cppcheck feature was not fully working and needed a overhaul, and at the
same time could be moved away from the main makefile to decrease the number of
export statements and shell calls required in that file.
Fix doxygen and verify targets

Ifdef statement for doxygen was not working. Verify target had ';' and the end
starting the recipe before first command resulting in wrong echos to stdout.
Merge branch 'performance'

Some minor performance fixes mostly improving start up. NULL-build speed for a
small project twice as fast as before, though in number of hundreds of
milliseconds. Mostly due to the fact that the search for some commands was
moved to the build makefile. Also using export statements seems to degrade
performance.

All-in-all these improvements are irrelevant for a larger project containing
+100 source files. But improvements are improvements.