switch dependencies install from pear to compose

Using compose tool is easier to manage
include composer source code

This has been bootstrapped from the tools/download_composer.sh script.
unit tests rewriting final step
add missing composer vendor directory
ignore vendor relatively to this directory

This was ignoring the composer's vendor directory.
check for clearsavepoint property

This allow to only do Update and Install testsuites when database
structure has been changed from upstream code.
update README about unit tests
add a basic customized Ant project

This xml file is used to override some Ant targets from the build.xml
and this can be used to run only one testcase from the testsuite.