DS-1820 Introduction of URL validators in SolrServiceImpl breaks .local urls

http://jira.duraspace.org/browse/DS-1820

When a URL like http://mypc.local/solr/search is entered as a search.server the URL validation fails. This is default behaviour of the Apache Commons URL validator but potentially unwanted.

I suggest creating an option toggling the URL validation. Default to true. (i.e. validationenabled) 
I'd prefer to not have a negative default config, can we unwind this a bit and make it solr.url.validation.enabled = false instead?