Documentation.

git-svn-id: http://h2database.googlecode.com/svn/trunk@5121 e6896862-9d19-0410-bfb3-e9fa5d50e656
MVStore changes: abstract storage to support off-heap storage; rename getSize to sizeAsLong; avoid importing java.beans package to speed up starting the JVM

git-svn-id: http://h2database.googlecode.com/svn/trunk@5122 e6896862-9d19-0410-bfb3-e9fa5d50e656