Allow to keep the build dir after succesful build

Set the option cleanupbuild to False to keep the build dir after a
succesful build. Can be helpfull for debugging purposes.
bump version to v1.13.0dev
return to original directory after executing a command in a subdir
make sure that 'module' function with either 'lmod' or 'LMOD_CMD' is accepted as matching with Lmod modules tool
fix bootstrap with Lmod
Merge pull request #908 from boegel/run_cmd_return

return to original directory after executing a command in a subdir
Module path guessing: added 'lib32' path
Merge pull request #912 from wpoely86/lib32

Module path guessing: added 'lib32' path
fix unit test for --allow-modules-tool-mismatch
check whether module is defined before undefining it
fix unit test that checks for module vs modules tool mismatch detection
allow mismatch of modules tool during stage 2 of bootstrap
useless to undefine 'module', subshells may get it redefined anyway
make sure modules/all subdir in install path already exists
Add custom repository type
Merge pull request #911 from boegel/fix_lmod

fix bootstrap with Lmod, fix issue with module function check
tweak command used in stage1 to determine EasyBuild version, only create modules path if it doesn't exist yet
fix github tests
Merge pull request #916 from boegel/github_tests

fix github tests
Merge branch 'develop' into fix_lmod