lib/template: move template related code to its own subdir
test_template_compile: Add a testcase for log_template_compile function

Main goal of this test is to help the refactoring the log_template_compile
monster function.

Signed-off-by: Juhasz Viktor <jviktor@balabit.hu>
Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>