Empty TestPlaceholderPath class in preparation of issue #54

* added empty Tests/capture/test_placeholderpath.h
* added empty Tests/capture/test_placeholderpath.cpp
* added Tests/capture/CMakeLists.txt
* modified Tests/CMakeLists.txt to enable the new test
* kept empty test testPrecess and empty test fixture testPrecess_data
4 jobs for !199 with feat54/step1 in 65 minutes and 58 seconds (queued for 72 minutes and 49 seconds)
detached
Status Job ID Name Coverage
  Build
passed #88100
build

00:12:06

 
  Test
passed #88121
build-and-test

00:47:51

passed #88102
build-appimage

00:06:00

failed #88101
build-and-test

01:00:02