Some .htaccess fixes

Here a small change I had to do to dropplets, to be able to install it at 2 web-hosters where I need to live with the default values for apache I get and .htaccess is the only thing I can configure. Still it shouldn't break any normal hostings I believe, since the difference is only, if default values don't match with what you expected before.

.....
The auto-generated .htaccess-file now always adds a RewriteBase and defines
a more strict rule for index to be index.php
This solves the problems by 2 web-hosts I've had were RewriteBase was required
even it was set to the root (/) and the default file wasn't index.php => it
worked only when set directly to "domain.tld/index.php" but not to "domain.tld"