More flexibility and first source options

The logger code can now be sourced with few available options that allow to customise some aspects. Furthermore, parts of the message can be highlighted using the --emph option of the logger functions. Refer to the CHANGELOG and to the README files for more information.

A first basic version

Since some already planned features have not yet been implemented, it is early for a major release. However, the BashLogger is working in its basic functionality and it makes sense to have a first v0.1 release.