Use http-conduit for url downloads by default, annex.web-options enables curl

* For url downloads, git-annex now defaults to using a http library,
  rather than wget or curl. But, if annex.web-options is set, it will
  use curl. To use the .netrc file, run:
    git config annex.web-options --netrc
* git-annex no longer uses wget (and wget is no longer shipped with
  git-annex builds).

Note that curl is always run in silent mode, since the new API for
download has a MeterUpdate and doesn't make way for curl progress
output. It might be worth writing a parser for curl's progress output
to update the meter when using it, but I didn't bother with this edge
case for now.

This commit was supported by the NSF-funded DataLad project.

Build/BundledPrograms.hs

@@ -69,14 +69,6 @@ preferredBundledPrograms = catMaybes
 	, Just "rsync"
 #ifndef mingw32_HOST_OS
 	, Just "sh"
-#endif
-#ifndef mingw32_HOST_OS
-#ifndef darwin_HOST_OS
-	-- wget on OSX has been problematic, looking for certs in the wrong
-	-- places. Don't ship it, use curl or the OSX's own wget if it has
-	-- one.
-	, ifset BuildInfo.wget "wget"
-#endif
 #endif
 	, BuildInfo.lsof
 	, BuildInfo.gcrypt