issue 8: fix display of ASCII art regression

regression was introduced by refacto of silent mode, jirac_echo can not be used directly
test silend_mode variable directly in ASCII art methods
improve jirac_echo(): support any number of parameter

all parameters are forwarded to the echo command
ISSUE #9: use name if available in pom.xml, otherwise artifactId

factorise code retrieving the text of an XML node in a pom.xml file
modify xml parser command to support non existing node without displaying a warning message, works with xmlstartlet, must be tested under mac
Issue #15. Switch to MIT License.