reintegrate InlineStyle; fix processing of stati images

[bwl21]

I have updated my development branch to your recent refactoring:

• reintegrated InlineStyle
• reintegrated the fix for the static images
• follow the proposed layout in https://github.com/ainterpreting/mosaico-php-backend/issues/11,
  • moved the upload folder out of the installation folder
  • keep uploads, thumbnails and static strictly separated
• fixed the base path in editor.html
• added index.html again such that we can have a working environment (not sure if it is better to keep it or to leave it out)

I have trouble with the .htaccess. It did not work if the thing is installed in a subfolder. I did not commit my .htaccess though:

• need to set the Options - otherwise Apache claims that RewriteRule is not allowed
• need to set a RewriteBase - otherwise rewrite adds my system path to the rewritten url

my development server uses an alias such that the url is http:localhost:8080/mosaico, this alias refers to a subdirectory of the server root.

<IfModule mod_rewrite.c>
Options +SymLinksIfOwnerMatch +FollowSymLinks
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteBase /mosaico/backend-php/
RewriteRule ^(.*)$ index.php [QSA,L]
</IfModule>