* AutotoolsPackage: added configure_directory to permit build out of source. The configure script executable is now invoked with an absolute path. Modified a few packages accordingly.
* build_systems: functions returning directories are now properties
* build_systems: fixed issues with tcl and tk
* AutotoolsPackage: reworked recipe for autoreconf
* Rename packages
* Upcasing depends_on() in packages.
* Downcased extends('r')
* Fixed erroneously changed URL that had slipped through.
* Fixed typo
* Fixed link from documentation into package source code.
* Fixed another doc problem.
* Changed underscores to dashes in package names.
* Added test to enforce lowercase, no-underscore naming convention.
* Fix r-xgboost
* Downcase more instances of 'R' in package auto-creation.
* Fix test.
* Converted unit test packages to use dashes not underscores
* Downcase `r` in the docs.
* Update module_file_support.rst
Fix r->R for class R.
