* docs: Fix a few typos

There are small typos in:
- doc/versioning.md
- src/components/ble/NimbleController.cpp
- src/libs/mynewt-nimble/CODING_STANDARDS.md
- src/libs/mynewt-nimble/docs/btshell/btshell_GAP.rst
- src/systemtask/SystemTask.cpp

Fixes:
- Should read `milliseconds` rather than `miliseconds`.
- Should read `unnecessary` rather than `uncesseray`.
- Should read `target` rather than `tharget`.
- Should read `project` rather than `projct`.
- Should read `preferred` rather than `prefered`.
- Should read `functioning` rather than `functionning`.
- Should read `forever` rather than `forver`.
- Should read `existing` rather than `exisiting`.

* Add the following compilation flags:
 * -fno-exceptions and -fno-non-call-exceptions : disable exception handling
 * -fno-rtti : disable run time type information (needed by dynamic_cast, for example)

These flags reduce the binary size by about 100KB!

Also, -fstack-usage generate debug info (not in final binary) to allow tools like Puncover to do a stack analysis.

* Remove unused CMake variables in CMake_nRF5x.cmake (duplicated in src/CMakeLists.txt).
Replace -O0 by -Og in DEBUG builds. This generates a smaller binary (small enough for the internal memory) that is debugger friendly.

Update documentation.
Remove Asserts when starting advertising to prevent crash (known bug).
Set version 0.5.0.

Advertising is working.

Work In Progress!!!