Optimize SVG files

See #341

First step was to save from Inkscape in optimize SVG format.
The used parameters are the following:
  * Simplify colors     -> true
  * Style to xml        -> true
  * Group collapsing    -> true
  * Enable id stripping -> true
  * Embed rasters       -> true
  * Keep editor data    -> false
  * Enable view boxing  -> false
  * Strip xml prolog    -> true
  * Set precision       -> 5
  * Indent              -> None

Second step was to edit the file and remove meta-data, title, extra carriage return and unnecessary namespaces.
Merge pull request #450 from aledeg/svg

Optimize SVG files
Sharing optimization

Change the storage and display of sharings to improve the time needed to generate the page.
Instead of looking for a default value when displaying the sharing links, they are added
during the configuration.
Change test
Add a test to avoid warnings in log
Change test on URL parameter
Merge branch 'share' of https://github.com/aledeg/FreshRSS into share

Conflicts:
	app/Models/Configuration.php