Moving towards new API, plus misc changes.

- Version number bumped and changelog removed (in favor of git)
- Dependencies are now handled automatically (via libfind_package)
- *_PROCESS_LIBS and *_PROCESS_INCLUDES are usually not needed at all
- Needs moar testing
Release version 2.1. Automatic dependency tracking added.

- libfind_package rewritten
   * Now tracks dependencies in list ${<PREFIX>_DEPENDENCIES} for libfind_process to use
   * No longer defaults to QUIET, extra parameters (such as "QUIET") may be added as needed
- libfind_process now complains of _INCLUDE_DIRS or _LIBRARIES are specified for processing
   * These are not config options and thus are mishandled and should not be used
- Handling of find modules with no version information changed: now they are accepted but we still complain.
- Added some debug output that can be enabled via LIBFIND_DEBUG=1

Note: PROCESS_INCLUDES and PROCESS_LIBS are only needed if the package uses options other
than <PREFIX>_INCLUDE_DIR and <PREFIX>_LIBRARY. Package's own variables with those names
are implicitly included as well as anything that is used via libfind_package (even non-
standard names if the other module is based on libfind because we track the option names).