apachesolr 6.x-3.0-rc1

#1780200 by pwolanin: document basic auth in README.
#1811456 by jhedstrom: remove dsm() from code.
#1226274 by pwolanin: Fixes for schema.xml version numbering and organization.
#761990 by pwolanin, jhedstrom, Nick_vh, jpmckinney | morningtime: Fixed 400 Bad Status if URL length limit exceeded.
#1811364 by Nick_vh: Fixed Add newly created content type to the indexed bundles for all environments.
#1811456 by rupl: Fixed Improve documentation of addFilter in apachesolr.api.php.
#1794602 by Nick_vh, pwolanin | ppmr: Fixed Undefined index: path in ApacheSolrDocument->__get()
#1764334 by cpliakas, Nick_vh: Fixed Negative percentage of documents sent to the server for indexing.
#1807552 by Nick_vh, wimvds: Fixed Site and url wrong when indexing multilingual content (using i18n module).
#1759190 by Nick_vh, mkalkbrenner: Fixed obsolete form code?.
#1805516 by Nick_vh: Added Basic upgrade path for 6.x-1.x to 6.x-3.x.
#1806294 by Nick_vh: Allow the batch to be alterable.
#1806300 by Nick_vh: Separate out the creation of the document from the index process.
#1802288 by Nick_vh: Fixed Improve testing of node deletion.