[refactor] "property" is used for different things in EntityBase

The naming in EntityBase was quite confusing, since the term
"property" was used both for member variables annotated with
@Property/@PropertyName and for the methods ("getter") to access
or calculate their values.

Now the term "accessor" is used to denote the accessor methods
consistently, while "property" is reservered for the actual
property entities. The terms "getter"/"setter" have been replaced
both by "accessor".

Change-Id: Ifffec4c2f7e47e409f72cedf4af3bcceb6a0f538
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>
[rest] RestWriter: Support for rendering of java.lang.Number

Added methods for rendering of java.lang.Number derivatives, which
apply also to short, byte, BigInteger etc.

Improved some Javadoc comments not related to the new methods.

Change-Id: I646efbf6ca7c76a46bbecc43384119847ba425c0
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>
RestConverter#canConvert() should not be used anymore

RestConverter is currently still derived from
com.thoughtworks.xstream.converters.Converter, but this will not
be true anymore soon. Therefore, the canConvert() method should
no longer be used.

Change-Id: I9fd770a0c1d07872bbd026c0b63b6a603363ac75
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>