imagej-maven: The CopyJarsMojo is not really an AnalyzeMojo

This was a left-over of an earlier experiment to re-use a large part
of the maven-dependency-plugin, which turned out to be infeasible.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
imagej-maven-plugin: switch from an explicit parameter to an implicit one

Earlier, we required the explicit configuration parameter
'imagejDirectory' for the 'copy-jars' goal. However, this requires
everybody who wants to use this goal to specify the configuration
explicitly at least in the root POM, which in turn requires the whole
<build><plugins><plugin>...</plugin></plugins></build> dance.

Instead, we switched to a parameter called 'imagejDirectoryProperty'
which refers to the name of a property specifying the location of the
ImageJ.app/ directory, and we skip copying anything if that property
is not set or does not point to a valid directory.

That way, we can add this plugin and its two goals to the default
life cycle incurred by using the SciJava POM; developers who want to
install their plugin to their ImageJ.app/ directory can then specify
the location either explicitly in the pom.xml file, or conveniently
via the command-line, depending whether their ImageJ.app/ directory
is expected to be in the project directory structure or outside.

Example: assume you developed your own plugin outside of Fiji or
ImageJ2. Then you would build the plugin in your favorite development
environment, and once you want to upload it to your update site,
you would call something like:

	mvn -Dimagej.app.directory=/home/gene099/Desktop/Fiji.app/

to install the plugin and its dependencies into your Fiji directory.
After that is done, you can start Fiji and upload your plugin; the
update will ask you to upload any used dependencies so that your
users will install and update all the required libraries as well.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
imagej-maven-plugin: allow the ImageJ.app to be set on the command line

It is really convenient to call

	mvn -Dimagej.app.directory=/home/gene099/Desktop/Fiji.app

to have the artifact and dependencies be copied to the given directory,
without having to modify any configuration or asking for a specific
goal.

If both the pom.xml and the command line specify the property, the latter
takes precedence (to allow convenient overriding via the command line).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Remove the parent from imagej-maven-plugin's pom.xml

We want to make this plugin part of the default life cycle specified
in the SciJava POM.

Removing pom-scijava as a parent avoids a dependency cycle (which would
only be possible using different versions).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Bump the imagej-maven-plugin version to 0.1.0

For 1.0.0, this developer would like to support 'nar' projects as well
so that the ImageJ launcher can be installed, and later maybe even
native components.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
pom-scijava: integrate the imagej-maven-plugin into the default life cycle

This means that developers can now install artifacts and their
dependencies into ImageJ.app/ directory structures conveniently by
simply specifying the 'imagej.app.directory' property. Plugins --
identified by containing a 'plugins.config' file -- go into the plugins/
subdirectory, libraries into jars/.

This property can be specified in the <properties> block of the pom.xml
file; the ${rootdir} property set by imagej-maven-plugin's 'set-rootdir'
goal comes in real handy here.

The property can also be specified on the command line in case the
ImageJ.app/ directory is located outside the project and may vary
from developer to developer.

If the property is not specified or does not refer to a valid
directory, the 'copy-jars' goal is skipped.

This improvement was inspired by Kota Miura.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>