Upgrade MapDB to 1.0.3

MapDB is out of beta, so it makes sense to upgrade to a release version!

Some API was removed (likely set to reasonable defaults) in the
configuration of the DB. Updated as needed.
Stop overriding surefire argLine

Several things are improved by not overriding argLine:
* apple.awt.UIElement doesn't need to be set as it's set in parent pom
* by overriding this property, we were losing default memory settings
  (Xmx, Xms 512) in the parent pom. This would cause "optimal" settings to
  be determined. This value, based on the environment, might be too low
  for memory-dependent tests (such as the CacheServiceTests). So let's just
  rely on the parent pom's defaults.
* As we are no longer overriding the argLine, we can also now pass
  -DargLine=...  arguments to unit tests, as desired.

Most likely will fix #152 once and for all!

Signed-off-by: Mark Hiner <hinerm@gmail.com>
Fix the estimation of the remaining free memory

Java has a funny memory concept. It lets users specify a maximum amount of
RAM to use, but it does not allocate all of it at once.

Therefore, there are three different memory values relevant to our
estimate: the amount of memory *currently* allocated, the maximum memory
Java will try to allocate, and the remaining free of the *currently*
allocated memory. These three values are available via java.lang.Runtime's
totalMemory(), maxMemory() and freeMemory() methods, respectively.

What we are *actually* interested in, though, is the *maximal* amount of
remaining memory, including the one Java will only allocate when asked to.
Therefore, we actually need to use the formula free + max - total.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
DRY up the code to determine how much memory is available, still

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use MemoryTools *everywhere*

There is a completely arbitrary fraction in the plane separator now: we
ask wether a 16th of the available memory is enough to read the plane.

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