Refactor templates

[drahnr]

• split up template per project and use include to combine them dynamically
• matrix.yml file to configure the buildmatrix
• build sparse matrix based on files in filetree
• consider tera instead of askama compile time code generation
• refactor code base

[subversive-owl]

oh never mind, i see that this ticket more or less covers the refactor plan

(subscribing...)

[drahnr]

Some more work went into splitting things up a little: 81f968d