build: Make codenarc SH script work under Windows (Docker compose)

Depending on the user's config (esp. core.autocrlf), line endings may be changed in source files. In most cases, this isn't an issue, but in Shell script file, the carriage return character (CR) can cause issues in interpretation. This can be detected when trying to launch the docker-compose script and having the "‘sh\r’: No such file or directory" error message: the "\r" is the carriage return being interpreted as part of the command.

This commit fixes this by specifying that .sh files should always be checked out with LF endings, not CRLF. .bat files are additionally set with CRLF endings.

Additionally:

The tool_prepare-codenarc has been renamed to tool_prepare-condenarc.sh for consistency and so that the .gitattributes rule would apply to it without declaring it specifically. The documentation and build files have been updated accordingly.
The .gitignore has been adapted to allow .gitattributes and some comments have been added to explain the rules for non-experts gitters (especially since ! rules have been used).

green-code-initiative / ecoCode-android

build: Make codenarc SH script work under Windows (Docker compose) #37