Add support for generating documentation in various formats

Switch document generation targets to use new wrapper functions found
in emacs.d/cmf-org-export.el.  While here, add support for the
following formats:

 * Markdown
 * Texi

Miscellaneous updates include:

 * Update location of Emacs MELPA package repository
 * Fine-tune weather-metno-mode
 * I do not use the xlicense package, so remove it
 * Do not hose directory created by eshell mode
Add appropriate phony targets

Add phony targets for TXIDIRS as well as markdown and texinfo
documentation targets