Merge pull request #1042 from hpcugent/develop

release EasyBuild v1.15.0
add debug logging in modpath_extensions_for
fix path_to_top_of_module_tree to consider multiple paths to the top of the module tree
add unit test for checking load statements in imkl module under HierarchicalMNS
fix added unit test for Tcl-based module tools: don't use test modules that unload recursively and make 'purge' fail
fix broken tests
cleanup in GCC test module
fix typo in GCC test module
fix remarks
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
bump version to v1.15.1, update release notes
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
extend release notes w.r.t. PR #1049
Merge pull request #1048 from boegel/v1.15.x

bump version to v1.15.1, update release notes