Feature replace cmarkup with tinyxml2

[qjgn]

Merges feature branch which replaces CMarkup with tinyxml2.

This PR:

• Removes CMarkup related files
• Adds tinyxml2 as dependency for all of the projects (Used to only be required by the test project)

In order to separate the specific library from the serialization boiler plate, this PR:

• Adds Serializer and Deserializer as thin wrappers around tinyxml2
• Splits up and moves serialization boiler plate into SettingsSerializer and SettingsDeserializer files

In order to fix issues that impeded testing during development, this PR:

• Fixes build issues on master for gcc and mingw (string handling and unsupported pragma)
• Adds force plate calibration XML test data
• Fixes inconsistent boolean string literals in the serializer output True/true
• Removes support for customizing the number of decimal points for double and float
• Includes tinyxml2 dependency as a git submodule instead of using cmakes Fetch content feature

Completed feature branch PRs:
#70, #71, #72, #73, #74, #75, #76, #77, #78, #79, #80,
#81, #82, #83, #84, #85, #86, #87, #88, #89, #90, #91,
#92, #93, #94, #95, #96, #97, #100, #101, #102, #103,
#104, #105, #106, #107, #108

[OliverGlandberger]

Tests performed:

• Built using Linux / Ubuntu terminal on Windows:

• Built using mingw32 compiler on Windows:

• Built using CMake / Visual Studio, as well as ran the tests: