doc: add software requirements and architectural design

Documentation/OS/README

...ntation/OS/architecture/LEANOS-UVIE-ADD-001_Issue_0_2.pdf

Documentation/OS/architecture/architectural_design.tex

...S/architecture/images/OS_fundamental_architecture.graphml

...on/OS/architecture/images/OS_fundamental_architecture.pdf

Documentation/OS/architecture/images/OS_logical.graphml

Documentation/OS/demo/demo.tex

...ntation/OS/requirements/LEANOS-UVIE-SRS-001_Issue_0_2.pdf

Documentation/OS/requirements/images/OS_logical.graphml

Documentation/OS/requirements/images/OS_logical.pdf

Documentation/OS/requirements/software_requirements.tex

Documentation/OS/shared/bibliography.bib

...n/OS/shared/fonts/MyriadPro-SemiCondensed-bold-italic.otf

...entation/OS/shared/fonts/MyriadPro-SemiCondensed-bold.otf

...tation/OS/shared/fonts/MyriadPro-SemiCondensed-italic.otf

...ntation/OS/shared/fonts/MyriadPro-SemiCondensed-light.otf

...ation/OS/shared/fonts/MyriadPro-SemiCondensed-regular.otf

...tion/OS/shared/fonts/MyriadPro-SemiCondensed-semibold.otf

Documentation/OS/shared/fonts/MyriadPro-bold-italic.otf

Documentation/OS/shared/fonts/MyriadPro-bold.otf