Advanced logging

[Schneegans]

This PR adds spdlog as our main logging library. The logger will print colourful messages to the console and store it's messages in a file called cosmoscout.log.

You can print messages simply with code like this: spdlog::info("The awnser is {}!", 42);

For each library / plugin of CosmoScout VR a separate default logger is created. This way, the
name of the library / plugin can be automatically prepended to the message.

• Advanced logging csp-fly-to-locations#4
• Advanced logging csp-trajectories#4
• Advanced logging csp-stars#4
• Advanced logging csp-sharad#4
• Advanced logging csp-anchor-labels#3
• Advanced logging csp-measurement-tools#5
• Advanced logging csp-lod-bodies#9
• Advanced logging csp-atmospheres#5
• Advanced logging csp-simple-bodies#6
• Advanced logging csp-satellites#2
• Advanced logging csp-rings#3

[github-actions]

Pull Request Test Coverage Report for Build 3ff370ba47ab762447834ef18264225a0a8edd19-PR-117

• 54 of 132 (40.91%) changed or added relevant lines in 22 files are covered.
• 1341 unchanged lines in 24 files lost coverage.
• Overall coverage increased (+0.4%) to 4.518%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/cs-graphics/Shadows.cpp	0	1	0.0%
src/cs-gui/internal/RequestHandler.cpp	0	1	0.0%
src/cs-gui/internal/ScopedTimer.cpp	0	1	0.0%
src/cs-utils/convert.cpp	0	1	0.0%
src/cs-core/GuiManager.cpp	0	2	0.0%
src/cs-core/InputManager.cpp	0	2	0.0%
src/cs-graphics/internal/gltfmodel.cpp	0	2	0.0%
src/cs-gui/gui.cpp	0	2	0.0%
src/cs-utils/FrameTimings.cpp	0	2	0.0%
src/cs-gui/internal/WebViewClient.cpp	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/cosmoscout/Application.cpp	1	2.59%
src/cs-core/TimeControl.cpp	1	1.35%
src/cs-graphics/Shadows.cpp	1	0.6%
src/cs-gui/gui.cpp	1	26.92%
src/cs-gui/internal/DisplayHandler.cpp	1	6.67%
src/cs-graphics/TextureLoader.cpp	2	3.57%
plugins/csp-measurement-tools/src/voronoi/VoronoiGenerator.cpp	20	0.7%
plugins/csp-simple-bodies/src/Plugin.cpp	20	2.33%
plugins/csp-rings/src/Plugin.cpp	21	2.22%
plugins/csp-satellites/src/Plugin.cpp	25	1.96%

Totals
Change from base Build 3c49d47539f6247dd7d963c8cd5a23e2353a2d56:	0.4%
Covered Lines:	528
Relevant Lines:	11686

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💛 - Coveralls