[keycloak-dev] Resource versions for SNAPSHOTS builds

[Stian Thorgersen]

When running SNAPSHOT builds the resource version contains -snapshot, but
doesn't get updated. This is annoying since stale resources are cached. To
work around this I've sent a PR to replace -snapshot with the build time
[1].

Further, When KeycloakServer is ran directly from the IDE the build time
isn't updated so I made it change the build time to the execution time when
not ran from within Maven [2].

[1]
https://github.com/keycloak/keycloak/pull/4287/files#diff-54e8a0187ed2030b92bb214c12019a38R49

[2]
https://github.com/keycloak/keycloak/pull/4287/files#diff-04c94b7f1ce8f7df22b037f39aa258cdR112