Templatedocs: style guide / tips and tricks

[laurianvm]

docs/template/styleguide.md suggested content:

• header with provenance and usage info,
• indentation rules,
• naming suggestions for folders

docs/template/tripsandtricks.md suggested content:

• examples of usage of formatting
• turn tests (mapper, macro's, includes, ...) into documentation style

[marc-portier]

after some initial comments I am elaborating and restructuring into ./docs/feaures.md, ./docs/examples.md and ./docs/styleguide.md

will need some more attention though