increased version 1.5.0

Change-Id: I1ba6d06896cdba40830710710505b4e9a73cc78c
XsemanticsRuntimeSystem.env method

This method replaces the previous keyword 'env' in Xsemantics grammar
(before version 1.5.0).

It is useless to have such element in the grammar, since it has
exactly the same syntax of this Java method invocation.

Change-Id: I2f29ebf9bc3c5c72e670b34ed86a06667dfcd45e

Conflicts:
	plugins/it.xsemantics.runtime/.settings/.api_filters
updated api-baseline

Change-Id: Ifcffea4e2bc6b6bc6b730c70a8ca6367ddeb275a
env implemented as standard method call

Change-Id: Ia005e41fbe2f4806117a30962d647679c0572a0b
removed XLiteral from the grammar

Change-Id: I1ec80be8d672ec9f8d512d363f97a26969e5907c
moved commands files to a separate dir

Change-Id: Ic334d4645b89abf7f22cea0479bd0e04cd3bfd27