Aggregate multi-chunk streams of characters

See issue #13.
Avoid instantiating one StringBuilder per tag in the pom.xml

Instantiating an object takes only a small amount of time, yet we can
easily avoid the cumulative time by requiring only one instance of the
StringBuilder and reusing it all the time.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Release XML Handler after parsing the POM files

There is little use keeping the internal variables around that were
only required for parsing the POM files...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Move multi-project comment where it belongs

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Adjust multi-project comment to current situation

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'characters'

We used to be very dependent on .pom files being "not too large": a
DefaultHandler's characters(char[], int, int) method can be called
multiple times before endElement(String, String, String). A normal
symptom on MacOSX was that MiniMaven showed:

	Ignoring unknown OS family: un
	Ignoring unknown OS family: ix

while parsing miglayout-3.7.3.1.pom. The problem is that "un" is
just at the 2kB boundary of that 16kB-sized file.

This topic branch fixes this by combining the values of all the
character() calls between a startElement() and an endElement() call
into one, and passing that value to in the endElement() method to
the newly-introduced processCharacters() method.

This fixes https://github.com/scijava/minimaven/issues/13.

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