Moved Core Theme Logos to CSS

In order to make it easier for a user/developer to replace logos in the core theme, I removed the hardcoded `logo.svg` and `logo-wide.svg` from the html, and replaced them with `div`s that use css background-image instead.

This has multiple advantages:
1. The user can now use any filename they want for the logo.  They are no longer forced to use logo.svg or logo-wide.svg.
2. The user can now easily use a JPG, PNG or GIF logo instead of SVG (SVG's are awesome, but used by an unfortunately small percentage of web developers at the current time.  Most probably don't even know how to make an SVG…).
3. The user doesn't have to resort to hacking the core theme template files in order to use a different filename or file type.
4. Greatly simplifies documentation instructions for how to change the logos (http://owncloud.org/theming/).

Signed-off-by: Jake Wilson <jakew@huebnerpetersen.com>
Concatenate string in SQL instead of PHP
use doctrine to construct concat expression
cleanup and actually execute the query
Change OC_Migrate from MDB2 to Doctrine
Merge branch 'master' into fix-5388-master
ref 3rdparty branch without MDB2 code
Merge branch 'master' into fix-5388-master
add support for nested groups
combineFilterWithAnd recently moved to Access
move nested group checkbox to directory settings
Merge remote branch 'upstream/master' into ldap_nested_groups
remove debug output
Merge branch 'master' into fix-5388-master
fix indentation
use identity test where appropriate
use camelcase variable names
_getGroupsByMember is a private function
Merge branch 'master' into fix-5388-master
Security Update: session fixation

Previous version is vulnerable to session fixation attack in some situations, guessing non-apache-module-php5 environment. Regeneration of session id should be done here.
Wrap the import/export db in a wrapper to make it compatible with the old style
Fix migration import of user files
Update user.php to fix duplicate session-duplicate