Removed documentation on false paths as per #2083

* document recommended usage of system blas/lapack

* update doc

* minor

* reword

* spack install : added --log-format option (incorporates test-install command)

fixes #1907

* qa : removed extra whitespace

* add filter_system_paths()

* filter system paths in set_build_environment_variables()

* two function: lib/inc + bin

* reverse order in bin

* fix order

* minor

* improvements of the code

* more cleanup

* alternative solution for filter_bins

* fiddle base alalazo's approach

* minor

* minor

* Fixed a bug causing config-specified compiler flags to be ignored.
Updated the compiler config so all flags are in a separate section.

* Updated the documentation for the `compilers.yaml` file spec.

* Implemented basic testing for the 'flags' section of compiler config.

* Fixed a few minor problems with the manual compiler config documentation.

* Don't clear LD_LIBRARY_PATH and friends from compiler wrappers

* remove debugging print

* Add new version property to handle joined version numbers

* Add unit test for new joined property

* Add documentation on version.up_to() and version.joined

* patch directive : fixed retrieval from urls fixes #1584

 - add support for 'gz' archives
 - fixed bugs with URL patches
 - updated nwchem

* patch directive : added checksum to UrlPatch

 - refactored classes in patch.py
 - updated nwchem

* patch directive : added caching

If Spec.dag_hash was called for the first time with a 'length'
specified, the cached hash was truncated. This ensures that the
full hash is cached.

* Removes the extra argument from Package.do_install while maintaining the changes in behavior pulled in #1603

* install : removed -i and -d shorthands (breaks backward compatibility)

* Change ':' to ','

* Add package bazel

* Add support for bazel-based builds

* Ignore GPG/PGP signatures/checksums when finding available downloads

* Remove duplicated basename