[IMPROVEMENT] Rework example queries for more readability

CVSAnalY shippes many example queries in a textfile.
Github offers the possibility to display the textfiles which was created in markdown format, very user friendly.

In this PR i`ve reworked the SQL example queries.

* Renamed file to markdown file extension
* Added Markdown format
* Changed all SQL keywords to uppercase
* Formatted the SQL queries for better readability

Here you can see how it looks like: https://github.com/andygrunwald/CVSAnalY/blob/markdown_queries/db/Queries.md