#506 Add LuceneSearch module with WebCrawler service.
#506 Divide Crawler functionality into two threads.
#506 Additional changes
#506 Add HtmlAgilityPack package.
LuceneSearch.csproj file fixed.
#506 Search refactoring.
#506 GoogleSiteSearchModule and SearchModule added.
#506 Implementing indexing worker.
Merge branch 'dev-search' of https://github.com/devbridge/BetterCMS into dev-search
#506 A few changes to indexing logic.
#506 Update page fetching
#506 Indexer Service test; Prevent existing pages from being indexed multiple times; Refresh outdated index.
#506 return text without HTML tags
Site search configuration added. #27 #506
Merge branch 'dev' into dev-search

Conflicts:
	Modules/BetterCms.Module.Root/RootModuleRegistration.cs
	Tests/BetterCms.Modules.Tests/BetterCms.Modules.Tests.csproj
#27 Search module: created search form and search result widgets
#27 Lucene search module modifications
#27 Lucene search module modifications
#27 Search module: snippet logic; created configuration value for using stop words;
#27 Created NuGet modules for search engines