JBIDE-16435 - NPE when starting/stopping LiveReload server when server with unknown type already exist

Preventing NPE when server runtime is null (ie, unknown)
JBIDE-16435 - NPE when starting/stopping LiveReload server when server with unknown type already exist
JBIDE-15966 - Livereload does not work with HTML files without <html>

Updated ScriptInjectionUtils

1. if there is node "head" - insert script at the end of the "head"
2. if there is no "head" and there is "body" - insert script at the end of the "body"
3. if there is no "head" and "body"and there is "html" - insert script at the end of the "html"
4. if there is no "head", "body" and "html" - insert script at the end of file