Add a Mojo (mvn plugin) to generate all UNIx command scripts from found commands

[rmannibucau]

If my module has these commands:

• foo --options=cfrf
• bar dummy --op=s
• ...

then I should get the following scripts:

• foo // usage: ./foo --options=cfrf
• bar-dummy // usage: ./bar-dummy --op=s

The scripts will support help:

./foo help

will execute the command help foo

and

./bar-dummy help

would execute the command help bar dummy

To find commands the Mojo will support:

• a list of classes (explicit listing)
• a list of folder (more or less same spirit as https://github.com/tomitribe/crest/blob/master/crest-maven-plugin/src/main/java/org/tomitribe/crest/maven/CrestCommandLoaderDescriptorGeneratorMojo.java#L93 so code should be shared probably)
• a list of dependencies (more or less same code as previously but iterating over the inputstreams of "*.class" of the entries of the JarFile)

Finally includes/excludes option and outputFolder will be added as configurable parameter to the Mojo.

Side note: it is probably a good idea to add a __find_java script (the name should just not conflict with commands) to share the logic of the JAVA finding then to get java command scripts can do:

proc_script_base=`cd $(dirname $0) && cd .. && pwd`
source "$(dirname $0)/__find_java"
$JAVA ....

Tip: https://github.com/apache/tomee/blob/master/tomee/apache-tomee/src/main/resources/tomee.sh#L24 or tomcat scripts can be used as model to find the right java command

For the classpath the same trick will be applied using another script not generated for the first version (another issue can be opened to generate a full assembly). It means the user will have to provider a __set_classpath script initializing CREST_CLASSPATH environment variable and scripts will just reuse this.