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.
add support for postinstallcmds, deprecate makeopts/premakeopts in favor of buildopts/prebuildopts
enhance unit tests w.r.t. postinstallcmds and deprecated makeopts
fix typo
fix checksums in unit tests
Merge branch 'develop' into postinstallcmds
make DEPRECATED_OPTIONS a dict, move handling of deprecated easyconfig parameters into a funtion
Merge branch 'develop' into cleanupbuild

Conflicts:
	easybuild/framework/easyconfig/default.py
Merge pull request #11 from boegel/cleanupbuild

sync with develop
fix conflict resolution fail
replace 'cleanupbuild' easyconfig parameter by '--cleanup-builddir' command line option, and enhance unit tests
Merge pull request #12 from boegel/cleanupbuild

replace 'cleanupbuild' easyconfig parameter by '--cleanup-builddir' command line option, and enhance unit tests
Cleanupbuilddir: make help message correcter
Merge pull request #853 from wpoely86/cleanupbuild

Allow to keep the build dir after succesful build
make sure that agithub python module can be imported without having simplejson installed
replace .error( with .raiseException( to make it generic (standard error in fancylogger doesn't raise an error)
Revert "replace .error( with .raiseException( to make it generic (standard error in fancylogger doesn't raise an error)"

This reverts commit b629b60f47c16223828610260ee103359691c16d.
Revert "make sure that agithub python module can be imported without having simplejson installed"

This reverts commit f34440baefd274537e1f8d443ad7f4083c5d9c78.
add robustness against agithub module not being imported because of ImportError, use decorator to check
fix guessing patch level for git diff patches by not stripping off b/ prefix, refactor to create guess_patch_level function, enhance unit tests