JVM args moved to JAVA_OPTS envvar (instead of JAVA_OPTS_APPEND)

[guidograzioli]

The role parameter keycloak_quarkus_java_opts now contains all arguments passed concatenated to the JVM, and it is used to value the JAVA_OPTS environment variable read be kc.sh.

By dafault, it takes the contatenation of two new arguments:

Variable	Description	Default
keycloak_quarkus_java_opts	Heap memory JVM setting	-Xms1024m -Xmx2048m
keycloak_quarkus_java_jvm_opts	Other JVM settings	same as keycloak
keycloak_quarkus_java_opts	JVM arguments; if overriden, it takes precedence over keycloak_quarkus_java_*	{{ keycloak_quarkus_java_heap_opts + ' ' + keycloak_quarkus_java_jvm_opts }}

Fix #185