change: make MDAbstractArray extend Serializable

...e/java/ch/systemsx/cisd/base/mdarray/MDAbstractArray.java

base/source/java/ch/systemsx/cisd/base/mdarray/MDArray.java

...ource/java/ch/systemsx/cisd/base/mdarray/MDByteArray.java

...rce/java/ch/systemsx/cisd/base/mdarray/MDDoubleArray.java

...urce/java/ch/systemsx/cisd/base/mdarray/MDFloatArray.java

...source/java/ch/systemsx/cisd/base/mdarray/MDIntArray.java

...ource/java/ch/systemsx/cisd/base/mdarray/MDLongArray.java

...urce/java/ch/systemsx/cisd/base/mdarray/MDShortArray.java

...eTest/java/ch/systemsx/cisd/base/mdarray/MDArraytest.java