#117 configured install paths ignored in startup

[Diemo Schwarz]

jmax can't start when specific install paths are given
to ./configure.

Since a certain time, the architecture-independent
files are no longer installed into the datadir
$prefix/share/jmax (although this is still claimed by
./configure --help --- a corollary documentation bug),
but into libdir/jmax

When a libdir different from the default $prefix/lib is
given in configuration, JMaxApplication.java doesn't
find the root by itself, but crashes in
guessDirectories line 592 (see below).

When giving the root manually to jmax, it is not passed
to fts, and there is no way to specify the exact lib
and bin paths.

Crash log:

Exception in thread "main"
java.lang.StringIndexOutOfBoundsException: String index
out of range: -10
at java.lang.String.substring(String.java:1480)
at
ircam.jmax.JMaxApplication.guessDirectories(JMaxApplication.java:592)
at
ircam.jmax.JMaxApplication.start(JMaxApplication.java:512)
at
ircam.jmax.JMaxApplication.main(JMaxApplication.java:417)