Merge pull request #1047 from boegel/fix_path_to_top_of_module_tree

fix path_to_top_of_module_tree to consider multiple paths to the top of the module tree
fix HierarchicalMNS for cgoolf and goolfc toolchains
add definition of iompi toolchain
clean up code in HierarchicalMNS.det_toolchain_compilers_name_version
fix remarks
fix minor remark
fix indent
Merge pull request #1049 from boegel/hmns_goolfc_cgoolf

fix HierarchicalMNS for cgoolf and goolfc toolchains + add iompi definition
Merge pull request #1048 from boegel/v1.15.x

bump version to v1.15.1, update release notes
Merge branch 'v1.15.x'