Issues 305: don't overescape strings at extraction time

* We now only escape single quotes at extractions and leave other special characters alone (&\<>")
* We escape special characters at display time
* Utils::cleanSearch() renamed to Utils::cleanString() and no longer sanitize strings for security (use Utils::secureText())
* Searches for special characters such as &brandshortname; or \ now work, same for API
* Google and Bing links no longer include html entities
Merge pull request #350 from pascalchevrel/issue-305-better_ampersand_escaping

Issues 305: don't overescape strings at extraction time
Issue #352: additional installation checks
* Check that PHP is installed
* Use curl to download data snapshot if wget is not installed
* minor style cleanups
* exit 1 codes + use echored if errors
Merge pull request #353 from pascalchevrel/issue-352-additional_checks_in_dev-setup_script

Issue #352: additional installation checks