* use `--with-yang-installdir=DIR` to install Clixon yang files in DIR
* use `--with-std-yang-installdir=DIR` to install standard yang files that Clixon may use in DIR
* Default is (as before) `/usr/local/share/clixon`
* Added -p <dir> command-line option to all programs: backend, cli, netconf, restconf.
* Moved and updated all standard ietf and iana yang files from example and yang/ to `yang/standard`.
* Renamed example yang from example.yang -> clixon-example.yang