fix: use HttpClient for fetching tiles

[zarathourstra]

This fix removes the use of URLConnection for fetching tiles. We use HttpClient instead.
the HttpClient manages its own thread pool but keeping the attributes that configure the internal executor ensures a gentle polling
The client is configured with a 5 sec timeout

Tested on examples by changing dependency path to system targetting local jar built and it works. Hope it works on your side
The exception URISyntaxException related to url malformatting are thrown given that someone can provide custom tile provider

[zarathourstra]

One improvment to consider is to remove static on client and expose a method to change configuration for example by providing custom client
This will enable the flexibility discussed about in issue #127

[msteiger]

Thanks a lot - it looks good on the first glance. Will need to dig a bit deeper, but I'm really busy at work right now, so I might need a few days.

[richardeigenmann]

Please grab some christmas cookies and hide away somewhere quiet to merge the PR and push a new version. I'm a +1 for experiencing a broken UI. Please advise if there is anything I can do to help.

[msteiger]

Lots of things changed so it took some time, but I released 2.8.1 yesterday. This one will be next.

[msteiger]

This one is now next on my list .. thanks for your patience