Add section about string manipulation
Moved some of the existing conventions into the new section:
- variable declarations
- text strings
- UI text style
Update CONTRIBUTING.md with references to CodingStyle file
Signed-off-by: Jeremie Guichard <djebrest@gmail.com>
Add a note in CONTIRBUTING.md that imperative mood
is the preferred way to write commit messages.
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>