Changed grammar to support optional property sections

Signed-off-by: Alex Tugarev <telekom@tugarev.de>
Added conversion and serialization support for ValueTypes (STRING, NUMBER, BOOLEAN) to Thing DSL

Signed-off-by: Alex Tugarev <telekom@tugarev.de>
Merge branch 'thing-dsl-optional-config' of https://github.com/qivicon/smarthome into qivicon-thing-dsl-optional-config

Signed-off-by: Kai Kreuzer <kai@openhab.org>
Merge branch 'qivicon-thing-dsl-optional-config'