FileManager: introduce verbosity levels to optionally silence output

13 jobs from feature/filemanager-improvements in 6 minutes and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #55587
VS2013
VS2013-32-bit

00:00:56

passed #55586
VS2013
VS2013-64-bit

00:00:59

passed #55585
VS2015
VS2015-32-bit

00:01:21

passed #55584
VS2015
VS2015-64-bit

00:01:09

passed #55865
VS2017
VS2017-32-bit

00:01:18

passed #55864
VS2015
VS2017-64-bit

00:01:40

passed #55579
Linux
clang-c++11

00:02:38

passed #55581
Linux
cppcheck

00:00:24

passed #55588
Linux
doc

00:00:20

passed #55578
Linux
gcc-c++11

00:04:30

passed #55580
Apple
macos-c++11

00:01:32

failed #55583
VS2017
VS2017-32-bit

00:00:08

failed #55582
VS2015
VS2017-64-bit

00:00:12