add a hackish sanity_check_paths with comment for MUST change in TEMPLATE.eb

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
fix comment placement

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
fix sources line and clarify other bits

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
Merge pull request #329 from fgeorgatos/602_embrace_and_extend_TEMPLATE

add a template sanity_check_paths as MUST in TEMPLATE.eb