Facilitate use of secured Linux environments for application providers

* Transformed the proposal from issue #8 [1] to a proposal file
* Moved the Solution Rationale and Distributions Support sections to the Problem Statement, as these 'stages' are not yet reached (e.g. Ubuntu and openSUSE do not yet pledge to adhere to this specification, as there is no specification formed, yet)
* Added a State header with state "Problem Statement"
* Corrected the spelling of proper nouns (apparmor -> AppArmor, OpenSUSE -> openSUSE)

[1] https://github.com/LinuxStandardBase/lsb/issues/8