PEAR coding standards and minor bug fixes

Fixed the issues @Alan Knowles, @Till Klampaeckel and Ken Guest stated
(https://pear.php.net/pepr/pepr-votes-show.php?id=689):
* Fixed classes and files naming issues.
* Moved "examples" to the root directory.
* Fixed mismatching licenses..
* Moved Abstract Client global constant into the Client class.
* Added Unit Tests.

In addition, fixed some minor bugs and add lacked documentations in
files headdoc.
Revert "PEAR coding standards and minor bug fixes"

This reverts commit 621ae130a742d0010502ba0e7a05bb2ba34dbd9b.