Make swagger generators configurable

Make swagger generators configurable

Swagger generators use configurable base URL paths with defaults:
- BaseYangSwaggerGeneratorDraft02 uses "restconf"
- BaseYangSwaggerGeneratorRFC8040 uses "rests"
Defaults may be overridden per deployment scenario. This makes Swagger
document generator more flexible in out-of karaf deployment scenarios.

Change-Id: I5fdda329dd2911913137d25a48450a5e161af679
Signed-off-by: Juraj Veverka <juraj.veverka@pantheon.tech>
Signed-off-by: Jakub Morvay <jmorvay@frinx.io>
(cherry picked from commit 55e2fe2242c35ee2d20168b29f0bc97313327b17)