Merge branch 'master' into stable

[BH-353] Add Documentation for main targets

* clean up mimimu required cmake version
* fixes for release workflow

Add documentation for targets, fixes for cmake
and release workflow.

Merge branch 'master' into stable

[BH-353] Add minimal build target for BH

* add BellHybridMain
* fixing post review

Git automatically converts BellHybird as move from source/main.cpp to
prevent this and maintain "main.cpp" history adding new target as
separate commit.

[BH-353] Add minimal build target for BH

Introducing changes required for adding BellHybird target without
removing PurePhone.
Adden new targets:
* Pure (builds PurePhone and PurePhone.img)
* Bell (builds BellHybird and BellHybird.img)
* [PurePhone|BellHybrid]-[UpdatePackage|StandaloneImage)

[BH-360] Move TPLIB re2 to separate dir

Changed submodule directory and updated cmake scripts.
Updated paths in PureCoverage script and Doxyfile

Merge branch 'master' into stable

[BH-399] Cleaning

Cleaned to match newest master

[BH-357] Move protobuf to third-party dir

* Use the CMakeLists.txt from lib authors.
* Disable building libprotobuf in the all target.
* Disable warnings in the libprotobuf-lite target.

[BH-397] Move TPLIB parallel-hashmap

Changed submodule directory and changed way its linked,
in order to use target_link_libraries checkouted phmap
dependency to the newest revision which includes small
cmake fixes (see 031d214f2ce1973933abdf2a998d986ff8094d8e),
updated paths in PureCoverage script and Doxyfile

[BH-365] Move TPLIB (tinyexpr) to separate directory

Move library, amend CMAKE files

[BH-461] Move TPLIB minimp3 to separate dir

Moved minimp3 to third-party directory,
added our CMakeLists.txt with interface
library defined and upgraded include paths

[BH-359] Move TPLIB pugixml to separate dir

Changed submodule directory and updated cmake scripts and include paths

[BH-361] Move date to separate directory

Move date to separate directory

[EGD-6355] Adjust MuditaOS to be used with Secure Boot

The start address of the OS image adjusted to comply with HAB
Secure Boot. Proper SNVS initialization performed at system startup.
SNVS drivers updated to most recent version. Image signing can be
performed as a part of build process. See doc/secure_boot.md for
more info.

[EGD-6507] Enable per-module testing

Add per-module:
 - test build
 - test execution
 - coverage reporting (xml/html).

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>

[EGD-3469] Fix assets and image creation

Preparing and copying of assets to the image was unreliable.
Switched from cmake mechanism to rsync, making resulting
scheme universal and reducing output folder pollution.

[EGD-5567] Add code coverage reporting

Add HTML and XML code coverage report generation with gcovr.

Cleanup unittests list - add missing googletest-gui to the unittests
list; remove dead functional tests.

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>

[EGD-6242] Fix image generate dependencies

Currently image is not regenerated when boot.bin is changed.
This patch fix the issue.

[EGD-6204] Add version.json to the udate package

`versin.json` is required for update process. This commit puts it back
to update package