MiniMaven: fix parsing of -D<key>=<value>

By mistake, it took <key>=<value> for the key, not just <key>.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
MiniMaven: Treat 'system'-scoped dependency as optional

Otherwise, it will always complain about tools.jar...

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

This fixes two minor MiniMaven issues.

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